Honeywell T874 User Manual

Page 1

T874 Multistage Thermostats

APPLICATION

These thermostats and subbases provide low voltage control of multistage heating and cooling systems, including heat pump systems.

and Q674 Subbases

PRODUCT DATA

FEATURES

• T874 Thermostat has silent, dust-free mercury switches operated by coiled bimetal elements.

• Heat anticipator(s) are adjustable or fixed cooling anticipator(s) are fixed.

• Individual heat and cool levers and scales (most models) for temperature setting located on top of thermostat case.

• Cover thermometer on most T874 Multistage Thermostat models.

• Locking cover and locking lever screws available for T874 Multistage Thermostats.

• Versaguard™ Thermostat Guard or custom key lock thermostat guards available for T874 Multistage Thermostats.

• T874 Thermostat requires a Q674 Subbase.

• Q674 Subbase provides system and fan switching, wiring terminals and mounting base for T874 Multistage Thermostat.

• Adapter plate available for mounting Q674 on wall or

horizontal outlet box.

• Light-emitting diodes (LEDs) located on subbase for

easy reference.

• Up to three stages each of heating and cooling control

possible.

• Models with setpoint restrictions and locking cover

with no thermometer available for Department of Defense (DoD) and other special applications.

• Outdoor reset used on some models to improve

thermal performance.

Contents

Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Checkout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Understanding Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

Cross Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Wiring Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

SPECIFICATIONS

IMPORTANT

The specifications given in this publication do not include normal manufacturing tolerances. Therefore, this unit may not exactly match the listed specifications. This product is tested and calibrated under closely controlled conditions, and some minor differences in performance can be expected if those conditions are changed.

Super Tradeline®/Tradeline® Models

SUPER TRADELINE controls offer features not available on TRADELINE or standard models, and are designed to replace a wide range of Honeywell and competitive controls.

TRADELINE models are selected and packaged to provide ease of stocking, ease of handling, and maximum replacement value. Specifications of SUPER TRADELINE and TRADELINE controls are the same as those of standard models except as noted below.

Super Tradeline Models

T874 THERMOSTAT

T874D Thermostat. Provides two stages of heating and two

stages of cooling. Use with Q674A-F Subbases.

Y594D (T874D/Q674E/TG504A) Thermostat/Subbase/key

lock cover package. Provides two stages of heating and two stages of cooling. Includes a key lock cover for setpoint protection.

Y594G (T874G/Q674F) Thermostat/Subbase package for

heat pump. Provides two stages of heating and one stage of cooling. Automatic changeover in heat or cool mode. Available in beige or Premier White® color.

Y594R (T874R/Q674L) Thermostat/Subbase package for

heat pump. Provides two stages of heating and one stage of cooling. Manual changeover in heat or cool mode. Available in beige or Premier White® color.

Tradeline Models

T874 THERMOSTAT

• T874 TRADELINE models provide staged heat and/or cool operation. See Table 1.

Table 1. Heating and Cooling Stages.

Models ABCDEF

Heating Stages 1122—2

Cooling Stages 12122—

• T874A-F are standard models.

TRADELINE FEATURES:

• TRADELINE package with cross reference label and special instruction sheet.

• T874A,C model available with factory stops for DoD applications.

• T874A,C model available with adjustable temperature locking stops.

Q674 SUBBASE

Q674 switching subbases provide system and fan switching. See Table 2.

Table 2. System and Fan Switching.

Q674 System Fan

A Heat-Auto-Cool Auto-On

B Heat-Off-Cool Auto-On

C Off-Auto Auto-On

D None None

E Off-Heat-Auto-Cool Auto-On

F Em. Ht.-Off-Heat-Auto-Cool Auto-On

G Off-Auto None

J Em. Ht.-Auto-Off Auto-On

L Em. Ht.-Heat-Off-Cool Auto-On

SUPER TRADELINE FEATURES:

• SUPER TRADELINE package with cross reference label and special instruction sheet.

• SUPER TRADELINE model supplied with locking lever and locking cover accessories.

• Includes adjustable temperature locking stops.

• T874D replaces T874A-F TRADELINE or standard models.

TRADELINE FEATURE:

• TRADELINE package with cross reference label and special instruction sheet.

• Q674A-E,G are standard (non-heat pump) models. Q674F,J,L are heat pump models.

ORDERING INFORMATION

When purchasing replacement and modernization products from your TRADELINE® wholesaler or distributor, refer to the TRADELINE® Catalog or price sheets for complete ordering number.

If you have additional questions, need further information, or would like to comment on our products or services, please write or phone:

1. Your local Home and Building Control Sales Office (check white pages of your phone directory).

2. Home and Building Control Customer Relations

Honeywell, 1885 Douglas Drive North

Minneapolis, Minnesota 55422-4386 (800) 328-5111 In Canada—Honeywell Limited/Honeywell Limitée, 35 Dynamic Drive, Scarborough, Ontario M1V 4Z9. International Sales and Service Offices in all principal cities of the world. Manufacturing in Australia, Canada, Finland, France, Germany, Japan, Mexico, Netherlands, Spain, Taiwan, United Kingdom, U.S.A.

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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Standard Models

T874 THERMOSTATS

Models: See Table 3.

Electrical Rating: 24 to 30 Vac.

Switching: Coiled bimetal elements operate mercury

switches.

Temperature Adjustment: Heating and cooling setting

levers, with separate scales located on top of thermostat base. Common lever for heating and cooling on T874R; one cooling lever on T874E,V; and one heating lever on T874F,Q.

Dimensions: See Fig. 1.

Temperature: Scale Range: 42° to 88°F (6° to 31°C) stan-

dard; optional ranges available.

THERMOSTAT MOUNTED

ON SUBBASE

FRONT

5-5/8 (143)

SIDE

3/8 (10)

Thermometer Range: 42° to 88°F (6 to 31°C)

Changeover Differential: 4°F (2°C) minimum between heat-

ing and cooling (5°F [3°C] on T874W). Levers can be set apart for greater separation.

Interstage Differential:

Standard Models: Mechanical differential is 1°F (0.6°C)

between heating or cooling stages; operating differential is approximately 1.9°F (1°C) between stages in heating or cooling.

Special Models: See Table 3.

Finish: Beige or Premier White

finish.

Mounting Means: T874 Multistage Thermostat mounts on

Q674 Subbase. Subbase mounts horizontally on wall or outlet box. Mounts on vertical outlet box with optional 193121A Adapter Plate Assembly.

SUBBASE

3-9/32 (83)

HEAT COOL

50 60 70 80

FAN

AUTO ON

50 60 70 80

OFF

EM. HT. HEAT AUTO COOL

1-7/8 (48)

2-3/16 (56)

Fig. 1. T874 Thermostat and Q674 Subbase dimensions in in. (mm).

Optional Specifications (T874 Only):

Temperature scale ranges are 40° to 75°F (4° to 24°C) heat-

ing and 75° to 90°F (24° to 32°C) cooling with stop; 44° to 68°F (7° to 20°C) heating, 80° to 86°F (27° to 30°C) cooling; 6° to 29°C (43° to 85°F) Celsius scale; 3° to 22°C (38° to 72°F) and 26° to 32°C (78° to 90°F) cooling with stop.

Nonadjustable factory-added stop limits heating setpoint to

72°F (22°C) maximum and cooling setpoint to 78°F (26°C)

minimum. OEM customer personalization. Locking cover and locking lever (see Thermostat Accesso-

ries). Thermostat cover without thermometer. Adjustable locking temperature stops. Voltage heat anticipation for first or second stage heat or both.

See Table 3. Fast cycling on heating stage(s) for electric heat applications. C815A Outdoor Thermistor for improved performance on

specified models.

1-1/2

(38)

3-1/2

(89)

FAN

AUTO ON

OFF

EM. HT. HEAT AUTO COOL

5-1/8 (130)

3-7/16

(87)

M584

Thermostat Accessories:

Locking Cover and Locking Lever Assembly: Part no.

194559R with thermometer; 194559S without thermometer. See Fig. 2. Includes cover, screws, and Allen wrench for locking cover. The screws must be used to assure proper operation.

Adjustable Lever Stop: Part no. 4074ECK; includes lever stop

and screws.

Universal Versaguard™ Thermostat Guard: Includes wall-

plate, ring base, guard cover, tumbler lock, two keys and optional Honeywell logo insert. Double-wall construction provides extra measure of tamper-resistance. Tamperresistant lock; key cannot be removed without being in locked position. Vents in guard base allow airflow for optimum thermostat performance. See form 68-0104 for more information.

— TG511A1000: Clear cover. — TG511B1008: Opaque cover. — TG511D1004: Painted steel (off-white) cover. See

Fig. 2.

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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Key Lock Cover: Part no. TG504A replaces existing T874

cover. Mounts on T874 base and covers thermostat settling

— TG504A1025: Blank face, internal thermometer.

— TG504A1033: External thermometer. See Fig. 2. levers and subbase switches. Includes LED window and two keys. Should not be used with 193121A Adapter Plate.

194559R Locking Cover

with Thermometer

Allen Wrench

TG504A1033 Key Lock

Cover with External

Thermometer

TG511D1004 Includes

Painted Steel Cover,

Opaque Base and Wallplate

Fig. 2. T874 Thermostat accessories.

Table 3. T874 Thermostat Specifications.

Anticipation

Models and Options Replaces Applications

T874A—Standard and TRADELINE®.

System Stages

Heat Cool Other Stage 1 Stage 2 Stage 1 Stage 2

T872A Standard 1 1 — 0.1-1.2A — 0-1.5A —

Heating (Adj) Cooling (Fixed)

— 72°F/78°F (22°C/26°C)setpoint

stops with locking cover. — Adjustable anticipator set 0.4A. — Adjustable locking temperature

stops (TRADELINE®). — 72°F/78°F (22°C/26°C) setpoint

stops with locking cover, no

thermometer (for DoD

T874B—Standard and TRADELINE. T872B Standard 1 2 — 0.1-1.2A — 0-1.2A 0-1.0A

T874C—Standard and TRADELINE.

T872C Standard 2 1 — 0.1-1.2A 0.1-1.2A 0-1.5A —

— 72°F/78°F (22°C/26°C)set stops

with locking cover, no thermometer

(for DoDa). — 12°F (7°C) differential between

H1 and H2 stages (T874C1125).

— Fast cycling. 0.12-

0.6A

T874D—Standard and SUPER

T872D Standard 2 2 — 0.1-1.2A 0.1-1.2A 0-1.2A 0-1.0A

0.12-

0.6A

TRADELINE®. — Adjustable locking temperature

stops (SUPER TRADELINE).

T874E—Standard and TRADELINE. T872E 2-Stage Cool — 2 — — — 0-1.2A 0-1.0A

T874F—Standard and TRADELINE.

T872F 2-Stage Heat 2 — — 0.1-1.2A 0.1-1.2A — —

— Locking cover.

Department of Defense.

Changeover stage operates with heating.

Fixed voltage type anticipation.

Changeover stage operates with heating; a secondary changeover is provided in cooling switch.

Provides night setback used with standard T874 and timer-operated remote switching.

Manual changeover stage—use Q674B,L subbase.

Changeover stage operates with cooling.Q674 Subbases

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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

— Fast cycling. Electric Heat 0.12-

0.6A

T874G—Heat pump, cool changeover, with fast cycling.

T872G Heat Pump or

Standard

0-1.0A

0.12-

0.6A

0.1-1.2A 0-1.0A —

— Fixed anticipator for H2. 0.1-1.5A

— Fast cycling. 0.12-

0.6A

T874H—Use with Q674C. T872H Heat Pump or

Standard

T874J—Heat pump. None Heat Pump 2 1

T874K—Heat pump. None Heat Pump 2 1

0-1.0A

—0-1.0A—

0-1.0Ae0-1.5Ac0-1.0A

0.1-1.2A

0-1.5A

0-1.5A —

—

T874L—Heat pump. None Heat Pump 2 1 — 0.1-1.2A 0.1-1.2A 0-1.5A —

T874N—Heat pump, heat changeover.

T872N Heat Pump 2 1

0.1-1.2A 0.1-1.2A 0-1.0A —

T874P—Heat pump. None Heat Pump 2 1 — 0.1-1.2A 0.1-1.2A 0-1.5A —

T874Q—Night setback heating. T872Q Standard

T874R—Heat pump. T872R

T874S—Two-speed compressor heat

None Heat Pump 2 2

Heat Pump

pump.

— — 0.1-1.2A — — —

21—

0-1.5A

0.1-1.2A 0-1.5A —

0-1.2Ac0-1.2A

0-1.2A 0-1.0A

T874V—Standard. None Standard — 1 — — — 0-1.5A —

T874W—Heat pump and standard. — Night setback heating.

Department of Defense.

Changeover stage operates with heating.

Fixed voltage type anticipation.

Changeover stage operates with heating; a secondary changeover is provided in cooling switch.

Provides night setback used with standard T874 and timer-operated remote switching.

Manual changeover stage—use Q674B,L subbase.

Changeover stage operates with cooling.Q674 Subbases

T872W Heat Pump or

Standard

32—

0-1.2A

c,d

0-1.2A 0-1.0A

Models:

See Table 4.

Mounting: Designed to mount horizontally on an outlet box

or the wall. Adapter plate assembly available for mounting on a vertical outlet box (see Subbase Accessory).

Electrical Ratings:

Switch Contacts: 2.5A at 30 Vac (7.5A inrush).

Finish: Dark brown or gray.

LED Lights (Optional): 30 Vac.

Dimensions in in. (mm): 3-1/2 (89)height; 5-5/8 (143) width;

Switches: Two slide switches (one switch on Q674G and K;

5/16 (8) depth. See Fig. 1. no switches on Q674D) operated by levers. Switch position is shown on scaleplate.

Table 4. Q674 Subbase Specifications.

Switch Positions

Models and Options Replaces Application

Q674A—Standard and TRADELINE®.

Q672A Standard HEAT-AUTO-COOL AUTO-ON T874A-D

Use WithSystem Fan

— Indicator LEDs.

Q674B—Standard and TRADELINE. Q672B Standard HEAT-OFF-COOL AUTO-ON T874A-D

— Provision for fan relay operation from Heat Pump T874G,H,L,R

external fan switch (isolate G terminal). OVERRIDE-HEAT- AUTO-ON T874P

— Indicator LEDs. OFF-COOL

Q674C—Standard and TRADELINE. Q672C Standard OFF-AUTO AUTO-ON T874A-H,W

— Indicator LEDs. Heat Pump OVERRIDE-AUTO- AUTO-ON T874K,L,N

OFF T874P

Q674D—Standard and TRADELINE.

Q672D Standard None None T874A-F

— For use when subbase switching is not

required.

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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Q674E—Standard and TRADELINE. Q672E Standard OFF-HEAT-AUTO-

AUTO-ON T874A-D

COOL

Q674F—Two LED models. — EM.HT. light.

— Provision for AUTO fan operation in

EM.HT.

Q672F Heat Pump OFF-EM.HT.-HEAT-

AUTO-COOL

OFF-COOL-AUTO-

HEAT-EM.HT.

AUTO-ON T874C,D,G,N,S

AUTO-ON

Q674G—O and B terminals. Q672G Standard OFF-AUTO None T874A-F

Q674J—Provision for AUTO fan operation Q672J Heat Pump EM.HT.-AUTO-OFF AUTO-ON T874A,D,G,J

in EM.HT. EM.HT.-ON-OFF AUTO-ON

— Provision for outdoor thermistor. SUPL.HT.-ON-OFF AUTO-ON

Q674K—Standard. Q672K Standard OFF-HEAT-AUTO-

None T874F

COOL

OFF-WOOD-WOOD/

None

OIL-OIL

Q674L—Provision for AUTO fan operation in EM.HT.

— Indicator LEDs. SUPL.HT.-HEAT-

Q672L Heat Pump EM.HT.-HEAT-OFF-

COOL

AUTO-ON T874R,W

AUTO-ON

OFF-COOL

Q674N—Standard. Q672N Evaporative

Cooler

Q674P—Standard. Q672P Heat Pump SUPL.HT.-HEAT-

EVAP-COOL-OFF-

HEAT

AUTO-ON T874C

AUTO-ON T874G

COOL

Q674Q—Standard. None Fan Coil HEAT-OFF-COOL LO-MED-HI-

T874A

Q674R—Standard. — International symbols.

None Fan Coil OFF-COOL LO-HI-

CONT.

T874V

Q674S—Indicator LED. None Standard HEAT-COOL None T874C

Optional Specifications (Q674 Only):

Models available with up to four LEDs; for example, LEDs can

show EM. HT, AUX. HT, SERVICE, CHECK, FILTER, and LOCKOUT. See Fig. 3.

System switching marked HEAT-OFF/RESET-COOL for sys-

tems requiring impedance relay reset. Available on Q674B only.

G terminal isolated on heating to provide fan relay operation

from external low voltage fan switch (Q674B only).

Auto fan operation on both heat and cool.

T874 Thermostat with

One Setpoint Lever

T874 Thermostat with

Separate

Heatin

and Cooling Levers

Fig. 3. Heating, cooling levers and system LED indicators.

L terminal is used for system monitoring devices. Common R terminal for heating/cooling. Changeover in cool or heat mode for heat pumps. Auto fan in EM.HT. for heat pumps.

Subbase Accessory: 193121A Adapter Plate Assembly for

mounting on vertical outlet box. Assembly includes adapter ring and cover plate. Use to cover wall marks from replaced thermostat.

Q674 Subbase

with Four LEDs

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Page 7

MERCURY NOTICE

This control contains mercury in a sealed tube. Do not place control in the trash at the end of its useful life.

If this control is replacing a control that contains mercury in a sealed tube, do not place your old control in the trash.

Contact your local waste management authority for instructions regarding recycling and the proper disposal of this control, or of an old control containing mercury in a sealed tube. If you have questions, call the Honeywell Customer Response Center at 1-800-468-1502.

INSTALLATION

When Installing this Product…

1. Read these instructions carefully. Failure to follow them could damage the product or cause a hazardous condition.

2. Check the ratings given on the product to make sure the product is suitable for your application.

3. Installer must be a trained, experienced service technician.

4. After installation is complete, check out product operation as provided in these instructions.

CAUTION

Hazardous Voltage. Can damage heating/cooling system.

1. Disconnect power supply before beginning instal-

lation to prevent electrical shock or equipment damage.

2. Do not short across coil terminals on relay. This

can burn out thermostat heat anticipator.

3. To prevent interference with the thermostat link-

age, keep wire length to a minimum and run wires as close as possible to the subbase.

4. Do not overtighten thermostat captive mounting

screws because damage to subbase threads can result.

IMPORTANT

An incorrectly leveled thermostat will cause the temperature control to deviate from setpoint. It is not a calibration problem.

Location

Install the thermostat about 5 ft (1.5m) above the floor in an area with good air circulation at average temperature.

Do not mount the thermostat where it can be affected by: — drafts or dead spots behind doors, in corners or under

cabinets. — hot or cold air from ducts. — radiant heat from the sun, fireplace, or appliances.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

— concealed pipes and chimneys. — unheated (uncooled) areas such as an outside wall behind

the thermostat.

Mount Subbase

The subbase can be mounted on a vertical outlet box, horizontal outlet box or directly on the wall.

1. If the subbase is mounted on a vertical outlet box, order Honeywell part no. 193121A Adapter Assembly. See Fig. 4. The assembly includes an adapter ring, two screws and a cover plate to cover marks on the wall. Install the ring and cover plate on the vertical outlet box.

NOTE: For a wall installation, hold subbase in position and

mark holes for anchors. See Fig. 5. Wall anchors must be obtained from local hardware store. Be careful that the wires do not fall back into the wall opening. Set aside subbase. Drill four 3/16 in. (4.8 mm) holes and gently tap anchors into the holes until flush with the wall.

2. Pull wires through the cover plate (if used) and subbase cable opening. See Fig. 6.

3. Secure the cover plate (if used) and subbase with the screws provided. Do not fully tighten the subbase screws.

Level the subbase using a spirit level, see Fig. 7, and firmly tighten subbase mounting screws. The subbase mounting holes provide for minor out-of-level adjustments.

VERTICAL OUTLET BOX

HORIZONTAL OUTLET BOX

SUBBASE

SUBBASE MOUNTING SCREWS (2)

CAPTIVE MOUNTING SCREWS (2)

1 NOT INCLUDED WITH UNIT. 2 ACCESSORY PART AVAILABLE (193121A).

Fig. 4. Installing Q674 Subbase on outlet box.

MOUNTING SCREWS (2)

THERMOSTAT

COOL

COVER

50 60 70 80

COVER PLATE

THERMOSTA

M6009

HEAT

ADAPTER RING

50 60 70 80

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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

SUBBASE

SCREWS (2)

(UP TO 12)

F I S

)

WALL

WIRES THROUGH WALL OPENING

WALL ANCHORS (2)

M926

MOUNTING HOLES

MOUNTING

Fig. 5. Installing Q674 Subbase on wall.

All wiring must comply with local electrical codes and ordinances.

IMPORTANT

Use 18 gauge, solid-conductor wire whenever possible. If using 18 gauge stranded wire, no more than 10 wires can be used. Do not use larger than 18 gauge wire.

Follow equipment manufacturer wiring instructions when available. To wire subbase, proceed as follows:

1. Connect the system wires to the subbase as shown in the applicable diagram. A letter code is located near each terminal for identification. Typical terminal designation and wiring connections are listed in Table 5. The terminal barrier permits straight or wraparound wiring connection. See Fig. 7. The subbase can require one or more jumpers that may or may not be factory-supplied. See Fig. 8 and the wiring diagrams for specific terminals to be jumpered.

SPIRIT LEVEL

POST FOR MOUNTING THERMOSTAT (2)

MOUNTING HOLES (4)

WIRING TERMINAL

THERMOSTAT CABLE OPENIN

TO SPRING FINGER CONTACTS ON THE THERMOSTAT

M927

Fig. 6. Subbase components and leveling procedure.

Wire Subbase

Disconnect power supply before beginning installation to prevent electrical shock or equipment damage.

OR STRAIGHT

NSERTION–

TRIP 5/16 IN. (8 MM)

SUBBASE TERMINAL SCREW

BARRIER

FOR WRAPAROUND– STRIP 7/16 IN. (11 MM

M928

Fig. 7. Barrier configuration.

CAUTION

Equipment Damage Hazard.

Never install more than one wire per terminal unless using factory-supplied jumper with spade terminal.

2. Firmly tighten each terminal screw.

3. Fit wires as close as possible to the subbase. Push

excess wire back into the hole.

4. Plug hole with nonflammable insulation to prevent drafts from affecting the thermostat.

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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

JUMPER WIRE (SUPPLIED WITH SOME MODELS)

1 TWO ADJACENT TERMINALS SHOWN JUMPERED ARE FOR EXAMPLE ONLY. COMPARE WIRING DIAGRAM AND SUBBASE TO IDENTIFY TERMINALS TO BE JUMPERED.

M5899

Fig. 8. Jumper adjacent terminals for special system hookup using stripped wire 3/4 in. (19 mm).

For nonadjacent terminals and using jumper wire supplied with subbase.

Standard Terminal

Designation

Table 5. Terminal Designations

Alternate Designations or

Customer Specials Typical Connection

B Heating damper motor; changeover valve

E K Emergency heat relay

G F Fan relay coil

L System monitor

O R Cooling damper motor; changeover valve

R V Power connection to transformer (internally connected for heating

and cooling)

RC Power connection to cooling transformer

RH Power connection to heating transformer

W1 H1, R3 Stage 1 heating control

W2 H2, Y, R4 Stage 2 heating control

Stage 3 heating control

Y1 C1, M Stage 1 cooling control

Y2 C2 Stage 2 cooling control

Y3 Stage 3 cooling control

X X1,X2,C Clogged filter switch or common connection

T A Outdoor thermistor

L, C, H HSII control panel

PDefrost

O Momentary circuit, changeover

A, A1, A2, Z, C, L LEDs

Other terminal designations can be used that are not listed on this table. Refer to the hookup drawing and internal schematic for exact connections.

W3 controls the auxiliary heat like W2, and allows adding additional stages of auxiliary heat with outdoor thermostats while maintaining the proper second stage anticipation.

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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

78°F (26°C) MIN. COOL

Standard Terminal

Designation

Table 5. Terminal Designations

Alternate Designations or

Customer Specials Typical Connection

T External temperature readout, T relay

R1, R2 LO and HI speed fan relays

RS Cooling contactor

Y M Compressor contactor

Other terminal designations can be used that are not listed on this table. Refer to the hookup drawing and internal schematic for exact connections.

W3 controls the auxiliary heat like W2, and allows adding additional stages of auxiliary heat with outdoor thermostats while maintaining the proper second stage anticipation.

Outdoor Disconnect

The National Electrical Code requires the installation of a disconnect switch within sight of the outdoor unit of an air conditioner or heat pump. The switch is for the safety of any technician working on the unit. The technician can assure that the unit remains unpowered.

mounting screw and two locking screws with insulated heads. When installed, the stop brackets limit the movement of the T874 HEAT and COOL levers.

TO INSTALL:

1. Remove the thermostat cover by pulling the bottom edge of the cover upward until it snaps free of the mounting slots.

Install and Adjust Stop Brackets

The stop brackets should be installed only if there is a need to restrict the adjustable range of the heating and cooling temperature setpoint levers. If adjustable lever stops are desired, order 4074ECK Envelope Assembly, which contains two adjustable lever stop brackets, one brass insert, one

2. Turn to the back of the T874 Thermostat. Locate the hole for the brass insert in the plastic base below the LED window.

3. Push the brass insert into the hole with finger.

4. Turn to the front of the T874 Thermostat.

5. Place the two stop brackets in position with the tabs in

the slot between the HEAT and COOL levers. See Fig. 9.

HEAT LEVER

ADJUSTABLE LEVER STOP BRACKETS

HOLES FOR INSULATED LOCKING LEVER SCREWS

COOL LEVER

BRACKET SLOTS

ADJUSTABLE STOPS

Fig. 9. Range limiting and lever locking methods.

HOLE WITH BRASS INSERT

BRACKET TABS

MOUNTING SCREW

ADJUSTABLE LOCKING LEVERS

NONADJUSTABLE STOPS WITH LOCKING LEVER SCREWS 75°F (24°C) MAX. HEAT 75°F (24°C) MIN. COOL

NONADJUSTABLE D.O.D. STOPS 72°F (22°C) MAX. HEAT

M7626

6. Insert the mounting screw into the two slots in the stop brackets and attach to the brass insert. Tighten the screw to pull the brass insert into the back of the ther-

60-2485—8 10

mostat.

7. Loosen the mounting screw enough to free the stop brackets for adjustment.

Page 11

8. Move the HEAT and COOL levers to the maximum tem-

M956

perature desired.

9. Slide the stop brackets until one rests against the HEAT lever and the other against the COOL lever.

10. Firmly tighten the mounting screw.

11. If the HEAT and COOL levers are to be locked in place

at a specific temperature, use the two insulated head screws supplied instead of the two adjustable lever stop brackets.

CAUTION

Equipment Damage Hazard.

Do not use standard screws that provide metal-tometal contact with the stop brackets. Short circuit and potential equipment damage can result.

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

ALLEN RETAINING SCREWS (2)

Mount Thermostat

1. Remove the thermostat cover by pulling the bottom edge of the cover away from the base until it snaps free of the cover clip.

NOTE: The cover is hinged at the top and must be removed

by pulling up at the bottom.

2. Carefully remove and discard the polystyrene packing insert that protects the mercury switches during shipment.

3. If LED indication (EM.HT., CHECK, etc.) is to be used with the Q674 Subbase, install the preprinted insert under the thermostat setpoint scale. To install, push both thermostat setpoint levers to the far ends of the thermostat. Use index finger to gently pull out the plastic setpoint scale about 1/4 in. (6 mm). Position the desired preprinted insert in the space above the LED lights. Reposition setpoint levers.

4. Turn over the thermostat base and note the spring fingers that engage the subbase contacts. Make sure the spring fingers are not bent flat, preventing proper electrical contact with the subbase.

5. Set the heat anticipator indicator(s) to the respective current setting of each stage. See Set The Heat Anticipator section.

6. If the thermostat provides optional locking cover assembly, start the Allen locking screws in the cover with the wrench provided. See Fig. 10.

7. Note the two tabs along the top inside edge of the thermostat base. The tabs fit into corresponding slots on top of the subbase. Mount the thermostat on the subbase.

8. Align the two captive mounting screws in the thermostat base with the posts on the subbase. Tighten both screws. Do not overtighten screws or damage to subbase posts can result.

Fig. 10. Installation of locking cover assembly.

SETTINGS

CAUTION

Equipment Damage Hazard.

On systems using a gas valve, never apply a jumper across the valve coil terminals, even temporarily. This can burn out thermostat heat anticipator(s).

Set the Heat Anticipator

Move the indicator to match the primary control current draw. When using a T874 Thermostat with two stages of heating, set each heat anticipator to match its respective primary control current draw. If you cannot find the current rating on the primary control, or if further adjustment is necessary, see NOTE and use the following procedure to determine the current draw of each stage.

The current draw of each heating stage must be measured with the thermostat removed and power on to the heating system.

1. Connect an ac ammeter of appropriate range between the heating terminals of the subbase: a. Stage 1—between W1 and RH or R; b. Stage 2—between W2 and RH or R c. Stage 3—between W3 and RH or R.

2. Move the system switch to HEAT or AUTO.

3. After one minute, read the ammeter and record the

reading: a. Stage 1—__________A; b. Stage 2—__________A; c. Stage 3—__________A.

NOTE: If equipment cycles too fast, set the indicator to a

higher current rating, but not more than one-half division at a time, and recheck the cycle rate. Most conventional two-stage heating equipment is designed to operate at three cycles per hour per stage, and one-stage heating equipment at six cycles per hour, at 50 percent load conditions. When using the T874 Thermostat in heat pump systems, set the heat anticipator at 140 percent of the actual primary control current draw to reduce the cycling rate. See Fig. 11.

11 60-2485—8

Page 12

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Most heat pump systems should cycle 2-1/2 to 3 times per hour.

4. Hang the upper edge of the thermostat cover on top of the thermostat base and swing the cover downward until it engages with the cover clip.

STAGE ONE

ANTICIPATOR HEATING CONTROL

M506

STAGE TWO ANTICIPATOR HEATING CONTROL

.12

.15

1.2

.10

.12

.15

1.2

MOVE INDICATOR TO MATCH CURRENT RATING OF PRIMARY CONTROL

Fig. 11. Adjustable heat anticipator scales.

Temperature Setting

Move the heating and cooling levers to the desired comfort positions. See Fig. 12. On some models with two stages of heating or cooling, the same lever controls both stages. The minimum differential between heating and cooling setpoints is 4°F (2°C) (5°F [3°C]) on T874W.

If model has optional screws to lock temperature control levers, loosen these screws before making temperature adjustment; tighten the screws when levers are set at desired position.

STAGE 1 HEATING

STAGE 3 HEATING

HEATING LEVER

COOLING LEVER

STAGE 1 COOLIN

HEAT—heating system is automatically controlled by the

thermostat. Cooling system is off.

AUTO—thermostat automatically changes between heat-

ing and cooling system operation, depending on the indoor temperature.

COOL—cooling system is automatically controlled by the

thermostat. Heating system is off.

EM.HT.—emergency heat relay is automatically controlled

by the thermostat. Cooling system is off. Compressor is de-energized.

SUPL.HT.—supplemental heat relay is energized. Cooling

system is off. Compressor is de-energized.

WOOD—heating system is operating with only the wood-

burning stage.

OIL—heating system is operating with only the oil-burning

stage.

WOOD/OIL—wood and oil stages operate sequentially;

first the WOOD stage operates, then the OIL stage operates if the WOOD stage cannot handle the load.

EVAP—controls cooling system by water evaporation; see

equipment instructions for further information. OVERRIDE—night setback is disabled. ON—heating system is controlled by the thermostat. EM.

HT. or SUPL. HT. relay is not energized.

FAN SWITCH positions control fan operation as follows:

ON or CONT.—fan operates continuously. AUTO—fan operates as controlled by the thermostat in

heat pump systems or conventional cooling mode; fan

operates as controlled by the plenum switch in conven-

tional heating mode. LO—fan operates constantly at low speed. MED—fan operates constantly at medium speed. HI—fan operates constantly at high speed.

To move the subbase switches to the desired control positions, use thumb and index finger to slide the lever. The lever must stop over desired function indicator position for proper circuit operation.

Spring return momentary position switching feature is available on selected subbase models. On these models, the fan switch is positioned to the right of the system switch. By moving the fan switch to the far right and releasing it, the ON position circuit makes. The lever springs back on release. This position is not marked on the subbase.

STAGE 2 HEATING

STAGE 2 COOLING

CAPTIVE MOUNTING SCREWS (2)

M7625

Fig. 12. Internal view of T874W (three stages of

heating, two stages of cooling).

Subbase Setting

The subbase switching positions control the system operation as described below. SYSTEM SWITCH (see subbase for positions):

OFF—both the heating and cooling systems are off. If the

fan switch is at the AUTO position, the cooling fan is also off.

60-2485—8 12

Setting the Adjustable Differential

The adjustable interstage differential feature, on a selected T874D model only, can be identified by the scale and tension screw near the heating and cooling mercury switches. See Fig. 13. On this model, the number of degrees between the making of the first and second stage mercury bulbs is adjustable. This feature is especially useful if the first stage controls the comfort temperature, and the second stage controls the energy savings temperature. Timers, such as the S6005, for insertion between the first and second stage control points must be ordered separately.

Each mark on the scale represents 1°F (0.6°C) The differential is factory set at 2°F (1°C) the differential can be set as high as 12°F (7°C) To set the adjustable interstage differential, loosen the tension screw. See Fig. 13. Slide the adjustable scale to align with the number of degrees desired between stages. Use the lower edge of the tension screw bracket as a guide for alignment. In heating, slide the lever

wider apart for a larger differential, or closer together for a

Page 13

smaller differential. In cooling, slide the lever closer together

M937

for a larger differential, or wider apart for a smaller differential. While supporting the scale with hand, tighten the tension screw.

IMPORTANT

Support the scale with hand while tightening tension screw. See Fig. 13. Failure to do so can result in twisting and damaging bimetal coil.

HEATING SETPOINT LEVER

TENSION SCREW

SCALE

HEATING

HEAT

TENSION SCREW

ALIGN LOWER EDGE WITH SCALE

NOTCH 10°F

SCALE

50 60

1.2

SECOND STAGE (ADJUSTABLE) SWITCH

70 80

1.5

SLIDE LEVER WIDER APART FOR LARGER DIFFERENTIAL

FIRST STAGE SWITCH

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

CAUTION

Equipment Damage Hazard.

When the thermostat is used to control a two-stage heating or cooling system, the second stage mercury bulb must never make before the first stage bulb, or severe equipment damage could result. To prevent this problem, provide at least 2°F (1°C) differential between stage-one and stage-two make points. Example: in heating, if stage-one makes at 70°F (21°C) stage-two should make at 68°F (20°C) or lower.

Verify the Adjustment

Heating

Start with the heating setpoint lever all the way to the left. Slowly move the lever to the right, just until the first stage bulb makes (mercury rolls to the right side of the bulb). Note the setting on the temperature scale. Slowly move the lever to the right until the second stage bulb makes. Note the setting on the temperature scale. The difference between the two temperatures is the interstage differential, which should match the number set on the scale with the tension screw.

Cooling

Start with the cooling setpoint lever all the way to the right. Slowly move the lever to the left, just until the first stage bulb makes (mercury rolls to the left side of the bulb). Note the setting on the temperature scale. Slowly move the lever to the left until the second stage bulb makes. Note the setting on the temperature scale. The difference between the two temperatures is the interstage differential, which should match the number set on the scale with the tension screw.

CHECKOUT

COOLING

TENSION SCREW

ALIGN LOWER EDGE WITH SCALE

NOTCH 4°F

SCALE

1 EACH MARK ON THE SCALE REPRESENTS 1°F (0.6°C).

SLIDE LEVER CLOSER TOGETHER FOR LARGER DIFFERENTIAL

Fig. 13. Set adjustable interstage differential.

Heating

Move the system switch on the Q674 Subbase to HEAT or AUTO. Move the heat lever on the T874 about 10°F (6°C) above room temperature. See Fig. 12. Heating system should start and the fan should run after a short delay. Move the heat lever about 10°F (6°C) below room temperature. The heating equipment should shut off, and the fan should run for a short time, then shut off.

In heat pump applications, sometimes time delays are involved before the compressor and auxiliary heat are activated. This is due to a minimum-off timer, which prevents the compressor from restarting for five minutes from when the thermostat last turned off the compressor, or from when the system first received power.

Cooling

CAUTION

Equipment Damage Hazard.

Do not operate cooling if outdoor temperature is below 50°F (10°C). Refer to manufacturer recommendations.

13 60-2485—8

Page 14

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

TEMPERATURE OF THERMISTOR (°F)

M1590A

Move the system switch on the Q674 Subbase to COOL or AUTO. Move the cool setting lever on the T874 Multistage Thermostat about 10°F (6°C) below room temperature. See Fig. 12. The cooling equipment and fan should start. If the system has two stages of cooling, both stages should start. Move the cool lever about 10°F (6°C) above room temperature. The cooling equipment and fan should stop.

Fan

Move the system switch to COOL, OFF, or AUTO. If necessary, position both temperature setting levers so that the heating and cooling equipment are off. Move the fan switch to ON or CONT. The fan should run continuously. When the fan switch is in AUTO, LO, MED, or HI position, fan operation is controlled by the heating or cooling system.

Outdoor Reset Thermistor (Where Applicable)

If the system is supplied with a thermistor, it must be used; if not used, thermostat performance deviates radically from proper operation.

The proper thermistor operation must be verified to ensure the correct operation of the thermostat. Check thermistor operations as follows:

1. Disconnect the T wire on the subbase.

2. Use an ohmmeter to measure resistance between the

T wire and the A subbase terminal.

3. Take outdoor temperature at thermistor location and find the correct thermistor resistance on the Fig. 14 chart.

4. If the resistance measured in step 2 and the calculated resistance in step 3 vary by more than 15 percent, the thermistor requires replacement. Contact Honeywell or installing dealer for replacement packaged outdoor thermistor, part no. C815A1005.

Thermometer

The thermometer in your thermostat has been accurately calibrated at the factory. The thermometer should only need adjustment if it has been dropped or shifted due to mishandling.

If the setpoint lever and the thermometer reading do not agree, use the following procedure:

1. Remove the thermostat cover by pulling up from the bottom edge of the cover away from the base until it snaps free of the cover clip.

2. Set the thermostat cover on a table near an accurate thermometer.

3. Allow ten minutes for cover thermometer to sense area temperature; compare the readings. Be careful not to touch thermometer or breathe on it.

4. If the readings are the same, replace cover and put the system into operation.

5. If the readings are different, insert a small screwdriver in the thermometer slot and turn it until the thermometers have the same reading. See Fig. 15.

6. Replace thermostat cover and put the system into operation.

4600 4400 4200 4000 3800 3600 3400 3200 3000 2800 2600 2400 2200 2000 1800 1600 1400

THERMISTOR RESISTANCE (ohms)

1200 1000

800 600 400 200

-20 0 20 40 60 80 100 120 14

C815A THERMISTOR RESISTANCE R = 400 ohms ± 10% AT 77°F (25°C)

Fig. 14. Thermistor resistance chart.

CALIBRATION

Thermostat

T874 Thermostats are accurately calibrated at the factory.

They do not have provision for field calibration.

M5070

Fig. 15. Thermometer calibration.

UNDERSTANDING CIRCUITS

To understand wiring diagrams, it is important to know what all the symbols mean and how to trace the path of the circuits from the transformer. See Fig. 16 through 25.

Circuit descriptions and terminology are defined as follows: For standard heating-cooling circuits:

Auto changeover—refers to the presence of an AUTO

position in the system switching (EX: Q674E with OFFHEAT-AUTO-COOL switching). The thermostat automatically changes between heat and cool modes as indoor temperature changes.

Manual changeover—requires a system switch movement

to change mode (EX: Q674B with HEAT-OFF-COOL switching). T874D Multistage Thermostats with 2 heat or 2 cool switches are shown on most standard circuits. Most standard or TRADELINE® subbases (Q674A-E,G) can be used with T874A-F standard or TRADELINE

60-2485—8 14

Page 15

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

thermostats. The schematics can be field-modified as required (EX: if T874C is being used, eliminate second stage of heat).

For heat pump circuits:

Cool changeover valve—operates on cooling. The revers-

ing valve or relay is activated either by moving the system switch to COOL (manual changeover) or by a mercury switch that makes on a temperature rise (auto changeover).

Heat changeover valve—operates on heating. The revers-

ing valve or relay is activated either by moving the system switch to HEAT (manual changeover) or by a mercury switch that makes on a temperature fall (auto changeover).

System monitor relay—optional equipment on some heat

pumps includes an R4222P1065 or equivalent. This system monitor relay detects a malfunction in the compressor and indicates the malfunction by activating the EMERGENCY HEAT LED on the Q674 Switching Subbase. The system monitor relay is usually wired into the L terminal on the Q674.

Each mercury switch is identified by function:

H1—Stage 1 Heating. H2—Stage 2 Heating. H3—Stage 3 Heating. C1—Stage 1 Cooling. C2—Stage 2 Cooling. C3—Stage 3 Cooling. C/O—Changeover (heat pumps).

perature rise. Fixed anticipation is represented by a zigzag line and adjustable anticipation is a zigzag with an arrow. The resistance of the fixed anticipator is so large it limits current so that a system relay cannot be pulled in from a circuit path going through the fixed anticipator. The relay can be pulled in through an adjustable anticipator because its resistance is generally 0 to 5 ohms.

5. The center portion (the subbase) contains the switches. The fan switch is above the system switch. The small circles on the switch represent the maximum possible contacts available on the Q674 Subbase. The larger circles represent the switch positions available on this particular Q674, with the solid circle representing where it is actually switched on the diagram.

NOTE: Solid circles are not interconnected electrically.

At the right, the relays and contactors are shown, attached to the proper terminals. The terminals are represented by large circles with terminal designations in capital letters. See Table 3 for the meaning of each lettered terminal.

Sometimes power for a fixed anticipator is brought through an off system relay like the changeover relay shown in Fig. 20. This current is kept low by the high resistance of the fixed anticipator so that relay does not pull in.

KEY TO HOOKUP SYMBOLS

Each anticipator is identified and each switch affected is named (EX: H1 anticipator, C1 anticipator).

All T874 Multistage Thermostats use mercury switches. Each schematic indicates switch operation by being drawn in the open position with an arrow indicating operation with a temperature RISE or FALL.

One circuit has been selected that is typical of various models used with heat pumps. This circuit has been traced to illustrate the functions performed by these control systems.

Tracing Method:

1. Always begin at the system transformer or R terminal. You may want to draw the switch contacts in each switch position to aid in tracing. Colored pencils are helpful when only one copy of the circuit is available. See Fig. 16 for a description of the hookup symbols and Fig. 17 through 25 for typical hookups.

2. Completely trace only one circuit at a time (for example: heat or cool).

3. Connections are indicated by small dots at the point of intersection. If there is no dot, there is no connection.

4. The left portion of the circuit (the thermostat) contains

TRANSFORMER (24 VAC SECONDARY)

ELAY OR CONTACTOR COIL

MERCURY SWITCH

FIXED ANTICIPATOR HIGH RESISTANCE (TYPICALLY 5 KILOHMS)

ADJUSTABLE ANTICIPATOR LOW RESISTANCE (TYPICALLY 0 TO 5 OHMS)

Fig. 16. Key to hookup symbols.

RELAY/CONTACTOR CONTACT

TERMINAL

LED

ODT

OUTDOOR THERMOSTAT

EHR

EMERGENCY HEAT RELAY

RTD

TIME DELAY RELAY

DEFROST RELAY

CHP

PRESSURE SWITCH

LACO

LOW AMBIENT CUTOFF

M584

the mercury switches. The heat switches make on a temperature fall, and the cool switches make on a tem-

15 60-2485—8

Page 16

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

THERMOSTAT

H1/C1 ANTICIPATOR

FALL

H2 ANTICIPATOR

FALL

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

AUXILIARY HEAT LED AVAILABLE ON SOME MODELS.

FAN SWITCH

AUTO

SYSTEM SWITCH

EM. HT.

HEAT

OFF

COOL

SUBBASE

AUX. HT. LED (GREEN)

EM. HT. LED (RED)

SYSTEM MONITOR

LACO

SYSTEM COMPONENTS

ODT 1

RTD 1 EHR 1

ODT 2

EHR 2 RTD 3

COOL CHANGEOVER VALVE

COMPRESSOR CONTACTOR

(HOT) L1

RTD 2

RTD 1

FAN RELAY

EM. HT. RELAY

CHP

M5072A

Fig. 17. Internal schematic and typical hookup of a T874R Thermostat and Q674L Subbase in a heat pump application.

The thermostat provides two-stage heating and one-stage cooling manual changeover operates on cooling.

60-2485—8 16

Page 17

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

)

THERMOSTAT

H1/C1

H2 ANTICIPATOR

ANTICIPATOR

FALL

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

SUBBASE SYSTEM COMPONENTS

SYSTEM MONITOR

LACO

RTD 1 EHR 1

RTD 1

FAN SWITCH

AUTO

SYSTEM SWITCH

EM. HT.

HEAT

OFF

COOL

AUX. HT. LED (GREEN)

EM. HT. LED (RED)

ODT 1

ODT 2

EHR 2 RTD 3

CHANGEOVER VALVE

COMPRESSOR CONTACTOR

(HOT)

RTD 2

FAN RELAY

EM. HT. RELAY

CHP

M584

Fig. 18. Tracing the changeover relay circuit.

THERMOSTAT SUBBASE

H1/ C1 ANTICIPATOR

FALL

H2 ANTICIPATOR

FALL

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

FAN SWITCH

AUTO

SYSTEM SWITCH

EM. HT.

HEAT

OFF

COOL

AUX. HT. LED (GREEN)

EM. HT. LED (RED)

G O

Y B

RTD 1

SYSTEM MONITOR

LACO

SYSTEM COMPONENTS

ODT 1

EHR 1

ODT 2

EHR 2 RTD 3

CHANGEOVER VALVE

COMPRESSOR CONTACTOR

RTD 2

FAN RELAY

EM. HT. RELAY

CHP

L1 (HOT

M5841

Fig. 19. Tracing the heat 1 and anticipation circuit.

17 60-2485—8

Page 18

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

M5842

)

THERMOSTAT SUBBASE

H1/ C1 ANTICIPATOR

FALL

H2 ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

FAN SWITCH

AUTO

SYSTEM SWITCH

EM. HT.

HEAT

OFF

COOL

AUX. HT. LED (GREEN)

EM. HT. LED (RED)

G O

Y B

SYSTEM MONITOR

LACO

SYSTEM COMPONENTS

ODT 1

RTD 1 EHR 1

ODT 2

EHR 2 RTD 3

RTD 1

CHANGEOVER VALVE

COMPRESSOR CONTACTOR

RTD 2

FAN RELAY

EM. HT. RELAY

CHP

L1 (HOT)

Fig. 20. Tracing the heat 1 anticipation circuit.

THERMOSTAT SUBBASE

H1/C1 ANTICIPATOR

FALL

H2 ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

FAN SWITCH

AUTO

SYSTEM SWITCH

EM. HT.

HEAT

COOL

OFF

AUX. HT. LED (GREEN)

EM. HT. LED (RED)

G O

SYSTEM MONITOR

LACO

SYSTEM COMPONENTS

ODT 1

RTD 1 EHR 1

ODT 2

EHR 2 RTD 3

RTD 1

CHANGEOVER VALVE

COMPRESSOR CONTACTOR

FAN RELAY

EM. HT. RELAY

RTD 2

CHP

L1 (HOT

M5843

Fig. 21. Tracing the heat 2, anticipation and AUX. HT. LED circuit.

60-2485—8 18

Page 19

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

)

M5845

)

THERMOSTAT SUBBASE

H1/C1 ANTICIPATOR

FALL

H2 ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

FAN SWITCH

AUTO

SYSTEM SWITCH

EM. HT.

HEAT

OFF

COOL

AUX. HT. LED (GREEN)

EM. HT. LED (RED)

G O

SYSTEM MONITOR

LACO

SYSTEM COMPONENTS

ODT 1

RTD 1 EHR 1

ODT 2

EHR 2 RTD 3

RTD 1

CHANGEOVER VALVE

COMPRESSOR CONTACTOR

RTD 2

FAN RELAY

EM. HT. RELAY

CHP

M5844

L1 (HOT

Fig. 22. Tracing the emergency heat and EM. HT. LED circuit.

THERMOSTAT SUBBASE

H1/C1 ANTICIPATOR

FALL

H2 ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

FAN SWITCH

AUTO

SYSTEM SWITCH

EM. HT.

HEAT

OFF

COOL

AUX. HT. LED (GREEN)

EM. HT. LED (RED)

G O

SYSTEM MONITOR

LACO

SYSTEM COMPONENTS

ODT 1

RTD 1 EHR 1

ODT 2

EHR 2 RTD 3

RTD 1

CHANGEOVER VALVE

COMPRESSOR CONTACTOR

L1 (HOT

RTD 2

FAN RELAY

EM. HT. RELAY

CHP

Fig. 23. Tracing the cooling circuit.

19 60-2485—8

Page 20

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

)

THERMOSTAT SUBBASE

H1/C1 ANTICIPATOR

FALL

H2 ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

FAN SWITCH

AUTO

SYSTEM SWITCH

EM. HT.

HEAT

OFF

COOL

AUX. HT. LED (GREEN)

EM. HT. LED (RED)

SYSTEM MONITOR

LACO

SYSTEM COMPONENTS

ODT 1

RTD 1 EHR 1

ODT 2

EHR 2 RTD 3

RTD 1

CHANGEOVER VALVE

COMPRESSOR CONTACTOR

RTD 2

FAN RELAY

EM. HT. RELAY

CHP

L1 (HOT

M5846

THERMOSTAT SUBBASE

H1/C1 ANTICIPATOR

FALL

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

H2 ANTICIPATOR

FAN SWITCH

AUTO

SYSTEM SWITCH

EM. HT.

HEAT

COOL

Fig. 24. Tracing the auto fan circuit.

AUX. HT. LED (GREEN)

EM. HT. LED (RED)

OFF

G O

SYSTEM MONITOR

LACO

SYSTEM COMPONENTS

ODT 1

RTD 1 EHR 1

ODT 2

EHR 2 RTD 3

RTD 1

CHANGEOVER VALVE

COMPRESSOR CONTACTOR

FAN RELAY

RTD 2

EM. HT. RELAY

CHP

L1 (HOT

M5847

Fig. 25. Tracing the fan on circuit.

60-2485—8 20

Page 21

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

OPERATION

Heat Anticipation/Cool Anticipation

When controlling a heating unit with a thermostat, the temperature does not remain exactly at the thermostat setpoint, but varies within a certain temperature range. Heat anticipation is added to the thermostat to reduce this range.

The anticipator is a small resistive heater in the thermostat that heats when the system is on (heat mode) or off (cool mode). The heat produced by the anticipator raises the internal bimetal temperature slightly faster than the surrounding room temperature. The thermostat anticipates the need to shut off the heating system sooner than it would if affected by room temperature only.

There are two types of heat anticipation, adjustable and fixed.

Adjustable anticipation is also called current anticipation. See Fig. 26. The heater is in series with the mercury switch and heating primary. The pointer is adjusted to match the current draw of the primary control, and the correct amount of heat is added for proper cycle rates.

(HOT)

Heat anticipators add heat during the call for heat. Cooling anticipators are activated while the air conditioner is off. See Fig. 28. This heater makes the thermostat think it is warmer than it really is, and brings it on sooner than the bimetal alone would.

(HOT)

RISE

C1 ANTICIPATOR

STAGE 1 COOL RELAY

M582

Fig. 28. Internal cooling anticipation schematic.

Interstage Differential

The mercury switch of each stage of heat makes at a slightly different temperature; that is, the mercury makes the contacts of the first stage bulb at one temperature, and the second stage bulb at another temperature. The difference between these two temperatures is the interstage differential.

H1 ANTICIPATOR

FALL

STAGE 1 HEAT RELAY

M582

Fig. 26. Adjustable anticipation heater in series with load.

Fixed anticipation is also called voltage anticipation. See

Fig. 27. The heater is in parallel with the primary control and is not affected by the current draw of the primary. It establishes the proper cycle rate for any application.

(HOT)

STAGE 1

FALL

HEAT RELAY

H1 ANTICIPATOR

M582

Fig. 27. Fixed anticipation heater in parallel with load.

Interstage differential is the difference between the two make points when the bulbs are controlled by the heating of the bimetal and the action of the heat anticipator. The interstage differential is 1.9°F (1°C) between the stages of heating or the stages of cooling for most models.

Mechanical differential is the difference between the make and break points of each switch. The mechanical differential for the T874 is 1°F (0.6°C) between the stages of heating or between the stages of cooling for most models.

Droop

The addition of anticipator heat to the bimetal causes a control factor called droop.

As the weather grows colder, the heating appliance must operate longer and more frequently. More heat must be added to the bimetal. The bimetal now thinks it is warmer than it really is, and actual room temperature is controlled at a lower temperature than the setpoint indicates. At 100 percent heat load, this droop can be significant.

The C815A Outdoor Reset Thermistor is used in heat pump systems to minimize droop. Without some method of countering this situation, the occupant could notice the temperature offset.

Outdoor Reset

Some T874/Q674 models are intended for use with the C815A Outdoor Thermistor. The outdoor thermistor provides significantly improved thermostat performance when compared to conventional multistage thermostats. The C815A is usually located in the heat pump condensing unit outdoors.

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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

CAUTION

Equipment Damage Hazard.

Due to calibration techniques used for T874 Thermostats with outdoor reset, the C815A Thermistor must be wired into the system at all times. Failure to do so will result in serious degradation of performance.

Service and Replacement of C815A Outdoor Thermistor

To check and verify thermistor operation, perform the following steps:

1. Disconnect wire from T terminal on subbase.

2. Measure resistance with ohmmeter across the T sub-

base wire and X subbase terminal.

3. Take outdoor temperature measurement at thermistor location and find correct thermistor resistance on the chart in Fig. 29.

4. Compare resistance on the chart with measured resistance. Replace C815A if resistance varies more than 15 percent. Contact installing dealer for packaged replacement outdoor thermistor.

4600 4400 4200 4000 3800 3600 3400 3200 3000 2800 2600 2400 2200 2000 1800 1600 1400

THERMISTOR RESISTANCE (ohms)

1200 1000

800 600 400 200

-20 0 20 40 60 80 100 120 14

C815A THERMISTOR RESISTANCE R = 400 ohms ± 10% AT 77°F (25°C)

TEMPERATURE OF THERMISTOR (°F)

M1590A

A strip of four inserts is included with TRADELINE T874. Drop a strip into the recessed area behind the scaleplate so selected LEDs show. Make sure insert is completely seated in recessed area. Let scaleplate pop back; then set levers to desired position.

• FILTER LED lights when the filter is clogged and needs replacement.

• CHECK LED lights when something needs to be checked or done to maintain efficient operation of system. See heating system instructions for CHECK LED meaning.

• EM. HT. LED lights when the emergency heat is operating.

• SUPL. HT. LED lights when the supplemental heat is operating.

• LOCKOUT LED lights when the system is shut down and needs maintenance.

• AUXILIARY HEAT LED lights when the auxiliary heat is operating.

• SERVICE or MALFUNCTION LED can have several meanings. Consult heating system instructions.

LEDs cannot be replaced or added in the field.

LEDS

EM. HEAT

FILTER SERV.

AUX HEAT

50 60 70 80

COOL

M583

Fig. 30. T874/Q674 LED location.

Restricted Setpoint (DoD)

The Department of Defense (DoD) models are equipped with a restricted setpoint feature for fuel efficiency.

Fixed stops are factory-set so setpoint levers cannot be set above 72°F (22°C) on heating, or below 78°F (26°C) on cooling.

Fig. 29. Thermistor resistance chart.

Features

Two of the features of the T874/Q674 include LED indicators and restricted setpoint.

LED Indicators

The light-emitting diodes (LED) indicators on the subbase light on command when something specific happens in the system. See Fig. 30.

Up to four different LEDs are available. The thermostat has a clear lens window for viewing each LED. On TRADELINE models, a small insert is used so the LED function desired can be selected. This must be done during installation.

A blank insert is factory-installed in some T874 models. To remove it, push both temperature setting levers to the far ends of the thermostat. Use index fingernail to gently pull out the scaleplate a fraction of an inch. Turn thermostat upside-down, and the blank insert falls out.

60-2485—8 22

Applications

The T874/Q674 can be applied to standard residential systems for automatic or manual changeover, to commercial rooftop applications, or to heat pump applications.

Changeover on Standard Residential Systems

In a standard residential heating-cooling circuit, changeover between heating and cooling can be done either automatically or manually.

Automatic changeover is done by an AUTO position on the subbase system switch. See Fig. 31. When the switch is in the AUTO position, the thermostat automatically changes between heat and cool modes, depending on the indoor temperature.

Page 23

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

M5829

When enthalpy is low enough, the thermostat and a sensor tell the economizer damper to open to let in cool air from the outside. When enthalpy is high, the thermostat and sensor tell the damper to close. No more outside air comes in, so the air conditioner is used instead.

OFF EM. HT. HEAT

AUTO COOL

M582

Fig. 31. System switching for automatic changeover.

Automatic changeover is frequently used in areas where there are large temperature differences in 24 hours. Some uses for the automatic changeover feature are in the southern states (cool in the morning and hot in the afternoon) and in commercial applications.

Manual changeover requires a system switch movement to change the mode. See Fig. 32. Most manual changeover switches consist of HEAT-OFF-COOL choices. For heating, switch to HEAT. For cooling, switch to COOL. It is not automatic.

Manual changeover is often used in areas where the temperature is relatively stable between day and night.

OFF EM. HT. HEAT

COOL

Fig. 32. System switching for manual changeover.

Commercial Rooftop Application

The T874 can be used as part of a commercial rooftop application to run mechanical cooling.

An economizer is often used as part of a rooftop application to save on air conditioning. See Fig. 33.

Heat Pump Application

A heat pump system operates much like an air conditioner. However, the heat pump is capable of moving heat in two directions; from inside the home to outdoors for cooling, or from outdoors to inside for heating.

The heat pump can be controlled by separate relay/contactor components, which are energized or de-energized by the T874.

Changeover between heating and cooling for heat pump circuits can be accomplished either manually or automatically.

Manual changeover control requires a system switch movement to change the mode. The reversing valve is activated by moving the system switch to COOL for cooling or to HEAT for heating operation.

Automatic changeover is accomplished by one of the mercury bulb switches in the thermostat. On a system with automatic changeover on cooling, the changeover valve is energized by a mercury switch that makes on a temperature rise. On heating, the changeover valve is energized by a mercury switch that makes on a temperature fall.

A description of the methods used to control heat pumps follows.

Space Temperature Sensing Low Voltage Controls

Control systems for heat pumps usually utilize low voltage control circuits. The variety of control functions required and the relative complexity require a versatile and economical method of control. There are several interlocks and indication functions that would be more difficult and expensive to wire in line voltage circuits. Low voltage controls have the precision and flexibility needed.

OUTDOOR AIR

H205 OR H705 ENTHALPY CONTROL

RETURN AIR

DISCHARGE AIR SENSOR DOWNSTREAM FROM TH EVAPORATOR COIL

M5827A

Fig. 33. Typical commercial rooftop economizer

application.

Enthalpy is the temperature and humidity of the air. A more accurate analysis of the suitability for free cooling can be made by monitoring the enthalpy.

The thermostat used is a low voltage device that has good temperature sensitivity and several manual and automatic switching capabilities.

Two-Stage Thermostat

In most installations, the heat pump itself requires auxiliary heat, usually in the form of electric strip heaters, to carry the building heating load at design conditions. Since the heat pump is usually more efficient, the control strategy is to run the heat pump whenever possible and the auxiliary heat only when necessary—during very cold weather or if the heat pump fails. Usually the auxiliary heat is used only below the balance point (temperature at which the heat pump cannot handle heating load by itself).

A two-stage thermostat makes this possible. The two stages make sequentially as the temperature drops. There is a degree or two between stages so that the second stage (the

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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

one controlling the auxiliary heat) makes only when the heat pump alone cannot handle the load. That is how the strategy of using the most economical heat first is implemented.

Cycling Rate

Normally, thermostat anticipation is set to cycle a fossil fuel furnace about five or six times an hour (at 50 percent load). This provides a reasonable balance between comfort, stability and economy.

A heat pump, being a mechanical refrigeration system, should be cycled at a rate of 2-1/2 to 3 times an hour. With a T874, this is accomplished by setting the anticipator at the total current draw of the controlled device (the contactor and possibly the changeover relay or valve). Most likely, the compressor operates from the first stage of the thermostat.

The second stage normally controls the auxiliary heaters. This heat anticipator can be set for the current draw of the electric heat primary, and produces good control.

Voltage Anticipation

Although not a specific requirement for heat pumps, several models of the T874 have voltage heat anticipation instead of current anticipation.

With voltage anticipation, the amount of heat added to the thermostat is constant no matter which load is connected to it. The anticipator realizes a constant voltage and produces a constant amount of heat during the ON cycle. This allows the cycling rate to be designed into the thermostat. The heat pump manufacturer is assured of correct performance independent of later thermostat adjustments.

This is particularly important on the 3-stage T874. The additional stage means that more droop is introduced when the system is in operation. That is the reason the TRADELINE T874W is sold in a package with the outdoor sensor and the correct subbase.

Outdoor Reset—How it Works

The heater in the thermostat is connected in series with a thermistor sensor that measures outdoor temperature. See Fig. 34. In warm weather, the thermistor has very low resistance, permitting a large current flow in the heater, which generates a relatively large amount of heat in the thermostat.

In cold weather, the outdoor sensor has high resistance, which results in low current flow and little or no heat being added to the thermostat. This raises the control point, overcoming the effects of droop and interstage differential.

(HOT)

RESET HEATER

Fig. 34. Location of thermistor.

C815A OUTDOOR THERMISTO SENSOR

M582

Outdoor Reset

Outdoor reset, which a C815A Outdoor Thermistor makes possible, is sometimes applied in heat pump systems to help minimize the effect of the differential between stages. It takes 2°F (1.1°C) change in temperature to bring on the second stage and full heating. Added to a certain amount of droop under high loads, there can be a large offset between the setpoint and room temperature.

Without some method to counteract this situation, the temperature offset from the setpoint could be as much as 6°F (3.3°C) under high load conditions. It is not likely that the occupants accept this variation without making frequent thermostat setting changes.

Outdoor reset has the effect of raising the setpoint at cold outdoor temperatures. Then, even with a few degrees droop, the space temperature stays near the desired setting.

This is done by calibrating the thermostat high by 5°F (3°C)— the amount of expected offset. This offset compensates for differential and droop at high load factors so the thermostat switches at the setpoint. At warm temperatures, heat is added to the thermostat to compensate for this offset; at cold temperatures, the extra heat is automatically removed. The effect is the same as raising the setpoint as the outdoor temperature goes down.

Changeover

Changeover between heating and cooing can be accomplished either automatically or manually, depending on the application. Changeover can occur in heating or cooling.

The changeover valve is energized as long as the subbase function switch is in the appropriate position when manual changeover is used. If a system manually changes over on cooling, the valve energizes whenever the subbase switch is in the cooling mode.

One of the mercury bulb switches is used for control when the thermostat has automatic changeover. When the automatic changeover is in cooling, the changeover valve is energized when the first stage cooling switch makes. The second stage switch turns on the compressor.

It is more common with new equipment to find that changeover occurs with cooling; that is, the changeover valve is energized to produce cooling.

Whether automatic or manual changeover is used and whether the reversing valve is energized with cooling or with heating, a heat pump system can be controlled by the appropriate T874 Multistage Thermostat.

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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Low Temperature Lockouts

Some manufacturers of heat pumps have previously controlled their units so the compressor was locked out below a specified outdoor temperature. This was done because of the stress placed on the compressor by the very cold temperatures, and the fact that efficiency drops off at low temperatures.

Other manufacturers say that although efficiency is low at cold temperatures, the problem of starting the cold compressor is the most critical point. It is more important to keep the compressor running than to shut it off and try to restart it when the temperature warms up to +10°F (-12°C). Also the crankcase heater, which can run only when the compressor is off, compensates for the lower compressor efficiency. So, it is equitable to let the heat pump run even with a coefficient of performance (COP) slightly less than one, rather than to turn it off and have to run the crankcase heater.

NOTE: To determine the COP of a heat pump, use the fol-

lowing formula:

COP =

Btu Out/Btu we pay for or Btuh Capacity Unit Wattage x 3.413 Btu/Watt

Another factor favoring this control strategy is that newer heat pump designs maintain a level of efficiency even at outdoor temperatures well below zero. Some brands do not reach

1.0 COP until -25°F (-32°C).

Virtually all manufacturers now let the heat pump run continuously rather than lock it out at cold temperatures.

Heat Pumps with Dual Compressors

Staging residential sized heat pumps is a requirement that developed from the need to make heat pumps as efficient as possible. One of the methods used to improve overall seasonal efficiency is to reduce the amount of time the machine is operating in a transitional mode. Transitional mode is starting and stopping in addition to recovering from defrost. Under light loads, when the heat pump is cycling on and off, this can be a significant amount of time and can result in a significant efficiency reduction. Capacity control is one way to reduce the cycling rate and improve the efficiency.

Additional capacity control methods used on other refrigeration systems (unloading, multiple compressors) are not as likely to be seen on residential heat pumps.

With a single-stage heat pump, the compressor is normally controlled by the first stage and the auxiliary heat by the second stage. The T874G, N and R Thermostats are used for this purpose.

THERMOSTAT

HEAT 1

HEAT 2

COMP. STAGE 1

COMP. STAGE 2

OUTDOOR THERMOSTAT

AUXILIARY HEAT

M5838

Fig. 35. Two-stage heat pump with two-stage thermostat.

The outdoor thermostat is set at the balance point with both heat pump stages running. So if the heat pump can control the heating load down to +20°F (-7°C), the auxiliary heat comes on with the second stage of the compressor.

In effect, this control strategy changes the heat input of the second stage, depending on the amount of heat needed. Additional stages of auxiliary heat can be added with or without the control of more outdoor thermostats, See Auxiliary Heat section.

Another way to control a two stage heat pump is with a threestage thermostat. The T874W is designed for this application as well as others. See Fig. 36.

The advantage of this system is that no auxiliary heat is used until there is an actual demand from the controlled space.

THERMOSTAT

HEAT 2

HEAT 1

COMP. STAGE 1

COMP. STAGE 2

AUXILIARY HEAT

M5837

HEAT 3

Fig. 36. Two-stage heat pump with three-stage thermostat.

With a two-stage compressor, the two thermostat switches control the individual compressor stages. Auxiliary heat is controlled along with the compressor stage-two, by the thermostat second stage. It comes on with the compressor high speed if an outdoor thermostat—wired in series with it— is made. See Fig. 35.

Two speed Heat Pump

One way to control capacity is to use a two-speed compressor. The compressor runs at low speed for stage-one heating and cooling. The compressor runs at the low speed instead of cycling the heat pump on and off under some light load conditions.

The high speed is stage-two cooling. The compressor runs on high speed when loads increase so the low speed can no longer handle the cooling load. This reduces cycling rate and improves capacity.

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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

M5839

M5835

Defrost Control

In some regions, during half or more of the heating season, the outdoor coil operates below 32°F (0°C) Frost or ice builds up on the outdoor coil of a heat pump similarly to the frost buildup in a household refrigerator. Eventually, this accumulation of ice interferes with efficient heat transfer from the outdoor air to the coil and refrigerant. Defrosting is occasionally required to remove this ice, and restore the heat pump ability to absorb heat from the air.

Defrosting

A heat pump defrosts its outdoor coil by temporarily switching to the cooling mode, which causes hot gas from the compressor to be directed to the outdoor coil instead of to the indoor coil so the heat pump is taking heat from the home to warm up the outdoor coil. Defrosting is the greatest detriment to heat pump efficiency.

Defrost Control Functions

Besides changing over to the cooling mode, defrosting requires several more control initiated actions that follow.

OUTDOOR FAN

When defrosting has begun, it is standard practice to turn off the outdoor fan to speed up the melting process. A separate defrost relay is required to control that fan. See Fig. 37. Other contacts can be needed on the defrost relay to power the changeover valve or power part of the auxiliary heat.

CONTACTOR

Fig. 37. Outdoor fan with defrost control.

COMPRESSOR MOTOR

CONTROLLED BY DEFROST RELAY

OUTDOOR FAN MOTOR

(HOT)

TRANSFORMER

THERMOSTAT

HEAT 2

HEAT 1

DEFROST RELAY CONTACT

AUXILIARY HEAT RELAY

Fig. 38. Auxiliary heat with defrost control.

WHEN TO DEFROST

Timely defrosting is an essential component of effective heat pump operation. Failure to defrost often enough permits too much ice to accumulate on the coil. At the very least, this hurts efficiency; at worst, it results in compressor damage. Insufficient defrosting is a condition the heat pump manufacturer wants very much to avoid.

A 50 percent reduction in outdoor airflow is the maximum that would be tolerated. So the designer of a heat pump would select a control point that puts the system into defrost when airflow through the outdoor coil approaches half its normal level. Restricted airflow causes a greater load on the compressor; the outdoor coil runs colder, suction pressure is lower and the motor runs hotter.

At the other end of the scale, defrosting too often hurts the overall energy efficiency of the system. Consider that in terms of heating the building, defrosting is a big loss. Not only does the system stop heating, but it actually moves heat out of the building. If electric strip heat is used, it is a further waste because its COP is 1.0 and not the 2.0 or more COP realized if the heat is provided by the heat pump.

So, concern for equipment safety suggests fairly frequent defrosting while economy of operation argues for fewer defrost cycles. Since the equipment manufacturer chooses, the balance is usually tipped in favor of more frequent defrosting to avoid the possibility of damaging the compressor.

AUXILIARY HEAT DURING DEFROST

Most pump manufacturers bring on some auxiliary heat during defrost, although this is not a universal practice. Some rely on the second stage of the thermostat to call for auxiliary heat as needed. Since the heat pump is operating in the cooling mode to defrost, it is delivering cold air to the living space. Auxiliary heat is used to offset this cooling. It requires another normally open contact on the defrost relay. See Fig. 38.

60-2485—8 26

Auxiliary Heat

Except in warm climates, all air-to-air heat pump installations require auxiliary heat capability. Electric resistance heaters can provide this auxiliary heat.

The electric heaters (sometimes called strip heaters) usually are supplied in 5 kW units or strips (about 17,000 Btu). The indoor unit of the heat pump is designed to accommodate various electric heat units so it can be used in variously sized buildings in different parts of the country.

Two-Stage Thermostat

The most common heat pump control strategy is for the thermostat first stage to switch the compressor and the second stage to switch the auxiliary heat. See Fig. 39.

Page 27

THERMOSTAT

)

M5834

O T

HEAT 2

HEAT 1

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

The disadvantage of this system is that it can require several outdoor thermostats. Also, since the unit is operating most often at nearly full capacity, the thermostat is on longer which results in more droop, with a little more offset from the thermostat setpoint.

COMPRESSOR CONTRACTOR

AUXILIARY HEAT RELAY

CONTROLS AT 65°F (18°C

CONTROLS AT 63°F (17°C)

M583

Fig. 39. Auxiliary heat in two-stage thermostat.

This method keeps the auxiliary heat off until the heating load is large enough to demand 100 percent heat pump operation. That demand is measured by the thermostat and is the actual heat requirement of the space. The two-stage thermostat requires about a 2°F (1.1°C) room temperature drop to bring on the second stage.

Stage or Time Modulated Control

There are two different ways to control auxiliary heat, staged or time modulated control.

Outdoor thermostats are used to switch additional increments of electric heat into the thermostat circuit as the outdoor temperature gets lower. All increments of auxiliary heat are still controlled by stage-two of the thermostat but only if the outdoor temperature requires the additional capacity. See Fig. 40.

THERMOSTAT

HEAT 1

HEAT 2

In addition, the capacity is tied to theoretical load, based on heat loss calculations. Normally this is very close to the actual load, but there are times where the second stage is switched on too soon (no harm done) or too late (the building gets cold).

The T874 Thermostat produces time modulated control, which is the on time of the thermostat changing during each cycle as the load changes. The on time of the heating system is directly proportional to the heating load of the building. As an example of the quality of time modulated control, consider the typical gas furnace. It can have a capacity of 100,000 Btu (293 kW), which is controlled On-Off. The output is 100,000 Btu (293 kW) or nothing. A quality thermostat controls so closely that the occupants rarely detect changes in room temperature.

The same is true with 50,000 or 60,000 Btu (146.5 or

178.8 kW) of heat pump auxiliary electric heat. The T874 can provide the same high quality control.

This scheme also eliminates the need for outdoor thermostats and thus offers the manufacturer an opportunity to reduce unit cost. One disadvantage is that a thermostat jiggler can be demanding more kW of strip heat when chilly.

The method any particular manufacturer selects depends on which arguments it finds persuasive and the opinions of its distributors and dealers.

Three-Stage Thermostat

A definite improvement in quality of control and economy can be achieved with a three-stage thermostat (T874W), which is especially true with heat pumps using dual compressors.

Three-stage control permits both the heat pump and the

COMPRESSOR CONTACTOR

auxiliary heat to be tied directly to the demand of the controlled space. With a two-stage compressor, maximum (100 percent) heat pump operation is required before auxiliary

20°F

UTDOOR

HERMOSTATS

(-7°C)

5°F (-15°C)

AUXILIARY HEAT RELAY 1

AUXILIARY HEAT RELAY 2

AUXILIARY HEAT RELAY 3

heat is brought on.

Emergency Heat

Some provision is generally required to back up the compressor in the event of a failure during the heating season. In fact, it is quite common to find that local building codes or electric utilities require that a specified percent of the building heating requirements be available from emergency heat—a source other than the heat pump compressor. Almost universally, the

Fig. 40. Outdoor thermostats for auxiliary heat.

source is electric resistance heaters. Typically, the requirement is for 70 or 80 percent of the building heating needs.

The rationale for this system is that it very closely matches the system capacity to the heating load of the building. By calculating the heat loss of a building, the installing contractor can pick the theoretical outdoor temperature at which to permit each additional unit of electric heat to be operated by the second stage of the room thermostat.

Switching to Emergency Heat

Conventional heat pump control (thermostat logic) usually includes a manual subbase switch to bring on the emergency heat.

In one control strategy, the emergency heat relay is turned on by the EM.HT. selector switch on the thermostat subbase. The compressor is prevented from running. The electric heaters are cycled as they normally would be by the second stage of

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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

)

the thermostat. A set of contacts on the emergency heat relay is used to bypass each outdoor thermostat so that all electric heat is under immediate thermostat stage-two control. So the emergency heat relay simply bypasses the outdoor thermostats. See Fig. 41.

In the second method, the emergency heat relay is cycled directly by the thermostat mercury bulb. In this hookup, the relay is controlled by the thermostat first stage. The emergency heat relay energizes all of the auxiliary heat relays on a call for heat. See Fig. 42.

So the emergency heat is controlled by the first stage of the thermostat. The emergency heat relay energizes all of the electric strip heaters so the heat and the indoor fan come on together as soon as the first stage calls for heat.

With the first method, the fan remains on (being controlled by the first stage of the thermostat) and the electric heaters cycle on and off with the second stage.

In either case, a subbase indicator light is turned on whenever the function switch is in the emergency heat (EM.HT.) position.

THERMOSTAT

FUNCTION SWITCH

HEAT 1

HEAT 2

OUTDOOR THERMOSTAT

EMERGENCY HEAT RELAY CONTACT

COMPRESSOR

AUXILIARY HEAT RELAY 1

AUXILIARY HEAT RELAY 2

EMERGENCY HEAT RELAY

M5833

Fig. 41. Emergency heat relay that bypasses

the outdoor thermostats.

Crankcase Heat

In any mechanical refrigeration system, refrigerant tends to migrate to the coldest part of the equipment and condense there. In a heat pump, this coldest spot could be the compressor because it is usually outdoors. In addition, the oil in the compressor crankcase is capable of absorbing a high concentration of refrigerant. On compressor startup, there are two risks: (1) the liquid refrigerant, which is noncompressible, can be drawn into the cylinder, and (2) considerable oil can be entrained in the refrigerant and swept out of the crankcase through the changeover valve and dispersed in the piping and coils.

So the migration of refrigerant to the crankcase is undesirable because it can interfere with system lubrication and because the liquid refrigerant must be kept from going through the compressor.

Adding a crankcase heater creates enough temperature differential to prevent this migration because the compressor is no longer the coldest part of the system so refrigerant does not migrate to it.

Compressor Fault Relay

Another very simple method of detecting a compressor failure has been developed. It uses the voltage developed across the capacitor in a permanent split capacitor compressor motor.

The principle involved is that virtually all serious problems reduce the voltage across the motor capacitor. By carefully selecting the correct coil voltage, the normally closed relay does not pull in unless the proper voltage builds up across the capacitor, which brings on the SERVICE LED. See Fig. 43.

Here is how it works:

• On a call for cooling, the thermostat makes R to Y, the contactor coil is powered, and the compressor motor turns on.

• At the same time, the indicator light is energized.

• As the motor gets up to speed—about one second, the fault relay sees enough voltage to pull in. Its normally closed contact opens and the indicator light goes out.

• Anything that prevents the motor from running prevents the fault relay from pulling in.

COMPRESSOR MOTOR

FAULT RELAY

24 V

THERMOSTAT

FUNCTION SWITCH

HEAT 2

HEAT 1

EMERGENCY HEAT RELAY CONTACT

COMPRESSOR

AUXILIARY HEAT RELAY

EMERGENCY HEAT RELAY

M583

Fig. 42. Emergency heat relay that energizes all of the

auxiliary heat relays on a call for heat.

ONTACTOR

RUN

CAP.

START

RISE

THERMOSTATSUBBASE

M5831

L1 (HOT

LED

Fig. 43. Compressor fault relay schematic.

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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

CROSS REFERENCE

The following section lists the current T874 Trade replacements for T872 and T874 Multistage Thermostats. It also lists the Q674 Trade replacements for Q672 and Q674 Subbases.

All thermostats listed carry the Honeywell logo unless otherwise noted.

When using the Cross Reference Charts, refer to the following instructions:

3. The Description column identifies certain characteristics of the existing device.

4. The Trade Replacement column identifies the correct replacement device.

5. The Remarks column lists any characteristics or adjustments to be made on the Trade replacement model.

6. The Fig. No. column lists the wiring hookup used for the specific model number. The wiring diagrams follow the Cross Reference section.

7. Refer to the circuit illustration that corresponds with the appropriate number. This figure illustrates the internal electric circuit for the desired model number.

1. Locate and identify the existing thermostat and subbase model.

2. Refer to the Model Number column to find the model that matches the existing thermostat and subbase.

Table 6. T872-T874 Thermostat Cross Reference.

Model Number Description

T874 Trade

Replacement

T872A 1-stage heat, 1-stage cool

A1006 Standard OEM T874A1036

A1014 72-78°F (22-26°C) stop; locking cover; no

thermometer

T874A1010 Use T874A1176 for Dept. of

Defense (DoD) application.

A1022 Heat anticipator set at 0.45A T874A1036

A1030 0.4A heat anticipator setting T874A1036

A1048 TRADELINE T874A1036

A1055 AAF logo; locking cover T874A1036

A1063 Climatrol logo T874A1036

A1071 Lennox logo; 0.5A heat anticipator setting T874A1036

A1089 Melco logo T874A1036

A1097 Westinghouse logo T874A1036

A1105 Amana logo; 1.2A heat anticipator setting T874A1036

A1113 Trane logo T874A1036

A1121 Airtemp (Chrysler) logo T874A1036

A1139 Singer logo; no. 02005384 T874A1036

A1147 American Standard logo T874A1036

A1154 Carrier logo and color; no. HH07AT074 T874A1036

A1162 General Electric logo; no. AY28X097 T874A1036

A1170 Sears logo; no. 4291441 T874A1036

A1188 Command-Aire logo T874A1036

A1196 Singer logo; Celsius scale; no. 02005521 T874A1036

A1204 Carteret logo T874A1036

A1212 General Electric; no. AY28X114; 72-78°F

(22-26°C) stop

T874A1010 Use T874A1176 for Dept. of

Defense (DoD) application.

A1220 Singer logo; no. 050240-01 T874A1036

A1238 Celsius scale T874A1036

A1246 TRADELINE; locking cover and adjustable locking

T874A1150

lever stops

A1253 Trane Comfort Corp T874A1036

A1261 TRADELINE; 72-78°F (22-26°C) stop; locking

T874A1176

cover; no thermometer; meets DoD specs

When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.

Remarks

29 60-2485—8

Page 30

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 6. T872-T874 Thermostat Cross Reference.

Model Number Description

A1279 General Electric logo; no. AY28X114A; 75°F stop;

locking cover; no thermometer.

A1287 General Electric; no. AY28X097A; fan current

shunt for auto fan in heating; heat anticipator set at

0.4A.

T874 Trade

Replacement

T874A1010 Use T874A1176 for Dept. of

T874A1036/ Q674B1018

Defense (DoD) application.

Set thermostat stage 1 heat anticipator for total of fan and stage 1 primary control current draw.

A1295 Lennox; Celsius scale T874A1036

A1303 Lennox logo; no. 64A0601; meets DoD specs T874A1176

A1311 Envirotron special; Celsius scale T874A1010

A1329 Carrier logo; Celsius scale; no. HH07AT074C T874A1036

A1337 Square D; no. HCD-3; heat anticipator set at 0.2A T874A1036

A1345 TRADELINE; Celsius scale T874A1010

A1352 Heat anticipator set 1.2A T874A1036

A1360 Friedrich logo; heat anticipator set at 0.2A T874A1036

A1378 Wesco logo; heat anticipator set at 0.8A T874A1036

T872B 1-stage heat, 2-stage cool

B1005 Standard OEM T874B1019

B1013 0.4A heat anticipator setting T874B1019

B1021 TRADELINE T874B1019

B1039 Westinghouse logo T874B1019

B1047 American Standard logo T874B1019

B1054 Climatrol logo T874B1019

B1062 Carrier logo T874B1019

B1070 Trane logo T874B1019

B1088 Fedders logo T874B1019

B1096 Climatrol logo T874B1019

B1104 Carteret logo T874B1019

B1112 Singer logo; no. 050240-03 T874B1019

B1120 Celsius scale T874B1019

B1138 Singer logo; no. 02005711; locking cover and

T874B1019

lever.

B1146 Lennox logo; no. P-8-8895 T874B1019

B1153 Lennox logo; Celsius scale T874B1019

T872C 2-stage heat, 1-stage cool

C1004 Standard OEM T874C1018

C1012 Heat anticipator set at 0.4A T874C1018

C1020 72-78°F (22-26°C) stop; locking cover; no

thermometer; 42-88°F (6-31°C) setpoint range.

T874C1141 Use T874C1141 for Dept. of

Defense (DoD) application.

C1038 TRADELINE T874C1018

C1046 American Standard logo T874C1018

C1053 Friedrich logo T874C1018

C1061 Lennox logo; no. P-8-8896 T874C1018

C1079 Westinghouse logo; stage 1 heat anticipator set at

T874C1018

0.75A; stage 2 anticipator set at 1.2A

C1087 Fast cycle performance on both heat stages;

anticipator range 0.12-0.6A

T874C1018 Adjust anticipator faster for correct

performance.

C1095 Payne logo; no. 0.1-0.175 T874C1018

When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.

Remarks

60-2485—8 30

Page 31

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 6. T872-T874 Thermostat Cross Reference.

Model Number Description

T874 Trade

Replacement

Remarks

C1103 Amana logo; anticipator set at 1.2A T874C1018

C1111 Airtemp (Chrysler) logo T874C1018

C1129 Day and Night logo; no. 0.1-0.174 T874C1018

C1137 Fast cycle performance on both heat stages T874C1018 Adjust anticipator faster for correct

performance.

C1145 Rheem logo T874C1018

C1152 Ruud logo T874C1018

C1160 Climatrol logo T874C1018

C1178 Wesco logo T874C1018

C1186 Sears logo T874C1018

C1194 First Co. logo T874C1018

C1202 Carrier logo T874C1018

C1210 Carrier logo; Celsius scale T874C1018

C1228 0.4A heat anticipator setting T874C1018

C1236 Carrier logo; no. HH07AT070 T874C1018

C1244 Fraser-Johnson logo T874C1018

C1251 Trane logo T874C1018

C1269 Fedders logo T874C1018

C1277 Climatrol special T874C1018

C1285 Autogas logo T874C1018

C1293 Fedders logo T874C1018

C1301 Climatrol logo T874C1018

C1319 Command-Aire logo T874C1018

C1327 Melco logo; lock cover and levers T874C1018

C1335 Singer logo (Carteret) T874C1018

C1343 Singer logo; no. 050240-04 T874C1018

C1350 Celsius scale T874C1018

C1368 12°F (67°C) differential between heat 1 and

T874C1125

heat 2

C1376 AAF logo; locking cover; 72-78°F (22-26°C) stop T874C1018

C1384 Servel logo T874C1018

C1392 TRADELINE; fast cycle performance on both heat

stages.

C1400 72-78°F (22-26°C) stop; locking cover; no

T874C1018 Adjust anticipator faster for correct

performance.

T874C1141

thermometer; meets DoD specs

C1418 Solaron logo T874C1018

C1426 Lennox logo; no. 42C04; four LEDs None

C1434 Carrier logo; no. HH07AT070C; Celsius scale T874C1018

C1442 Goettl logo T874C1018

C1459 Goettl logo; used with Q672N1001, N1019 None

C1467 Lennox logo; Celsius scale T874C1018

C1475 Tappan logo; no. 080-13708-37 T874C1018

C1483 Fasco logo; no. 1230-8161 T874C1018

C1491 Lennox logo; no. 64A0501; locking cover; no

T874C1141

thermometer; meets DoD specs

When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.

31 60-2485—8

Page 32

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 6. T872-T874 Thermostat Cross Reference.

Model Number Description

T874 Trade

Replacement

Remarks

C1509 Fedders logo; used with Q672L1102 Y594R1425 Wiring differences (old=new): C=X,

K=E; remove Y-W1 jumper.

C1517 Climatrol logo; used with Q672L1102 Y594R1425 Wiring differences (old=new): C=X,

K=E; remove Y-W1 jumper.

C1525 Square D logo; no. HCD-2 T874C1018

C1533 Airtemp logo T874C1018

C1541 Airtemp logo; used with Q672L1102 Y594R1425 Wiring differences (old=new): C=X,

K=E; remove Y-W1 jumper.

C1566 TRADELINE; Celsius scale T874C1018 Replacement has °F scaleplate.

C1574 Whalen special; used with Q672B1269 None

C1582 Lennox; meets DoD None

C1590 Singer; 8°F (4.4°C) differential between stage

1 and stage 2

C1608 Singer logo; no. 02005784 8°F (4.4°C) differential

between stage 1 and stage 2

T874C1125 Replacement has 2°F (1° C)

differential between H1 and H2.

T874C1125 Replacement has 2°F (1°C)

differential between H1 and H2.

C1616 Celsius scale; stop set at 23°C None Add 4074ECK adjustable stop.

C1624 Heat Wave logo; no. 0360-116 T874C1018

C1632 York logo; heat anticipator set at 0.2A T874C1018

C1640 Heat anticipator set at 0.4A T874C1018

C1665 Wesco logo; heat anticipator set at 0.8A T874C1018

C1673 Wards logo; used with Q672B1285, B1293 Gas systems:

T874C1018/ Q674B1034

Electric systems: T874C1018/

Adjust anticipator faster for correct performance.

Q674B1075

C1681 Lechauffage Urbain logo; Celsius scale T874C1018

C1699 Duotherm logo; used with Q672E1068 or

Q672F1000

T874C1018 See subbase description for

replacement information.

C1707 Sigler logo; used with Q672N1027 None

C1715 Westinghouse logo T874C1018

T872D 2-stage heat, 2-stage cool

D1003 Standard OEM T874D1165

D1011 TRADELINE T874D1165

D1029 Westinghouse logo T874D1165

D1037 Climatrol logo T874D1165

D1045 Lennox logo; no. P-8-8897; used with Q672E1191. T874D1165

D1052 York logo T874D1165

D1060 Singer logo; no. 02005385 T874D1165

D1078 Rheem logo T874D1165

D1086 Rudd logo T874D1165

D1094 York logo; locking cover T874D1165

D1102 American Standard logo T874D1165

D1110 ITT logo T874D1165

D1128 Carrier logo T874D1165

D1136 No anticipator on stage 1 cool; used with

T874D1165

Q672C1029

When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.

60-2485—8 32

Page 33

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 6. T872-T874 Thermostat Cross Reference.

Model Number Description

T874 Trade

Replacement

Remarks

D1144 Carrier logo; no. HH07AT072 T874D1165

D1151 General Electric logo; no. AY28X098; 0.4 heat

T874D1165

anticipator setting

D1169 Airtemp (Chrysler) logo; used with Q672E1118 T874D1165/

Q674E1049

Wiring differences (old=new): A=W1; set H1 anticipator to 1.2A.

D1177 Trane logo T874D1165

D1185 Dunham-Bush logo T874D1165

D1193 Fedders logo T874D1165

D1201 Climatrol logo T874D1165

D1219 Command-Aire logo T874D1165

D1227 Singer logo; no. 02005522; Celsius scale T874D1165

D1235 Singer logo; (Carteret) T874D1165

D1243 Friedrich logo T874D1165

D1250 Singer logo; no. 050240-02 T874D1165

D1268 Airtemp logo T874D1165

D1276 Celsius scale T874D1165

D1284 Solaron T874D1165

D1292 Tokyo Carrier logo; no. HH07AT072C; Celsius

T874D1165

scale

D1300 SUPER TRADELINE T874D1165

D1318 General Electric logo; no. AY28X098A; fan current

shunt for auto fan in heating.

D1326 General Electric logo; locking cover 72-78°F

T874D1165/ Q674B1075

T874D1165 (22-26°C) stop; fan current shunt for auto fan in heating.

D1334 Lennox logo; Celsius scale T874D1165

D1342 Tappan logo; no. 080-13708-32 T874D1165

D1359 Singer logo; no. 02005740; Celsius scale; 6.6°C

differential between H1 and H2.

T874D1165 Only 2°F (1°C) differential between

H1 and H2.

D1367 Friedrich logo; no. 600-580-23 T874D1165

D1375 Singer logo; no. 02005713; Celsius scale; controls

None 2 separate heat/cool circuits; used with Q674G1017

D1383 TRADELINE; Celsius scale T874D1165

D1391 Singer logo; no. 02005712; controls two separate

None heat/cool circuits; used with Q674G1017

D1409 12°F (7°C) differential between H1 and H2 T874D1165

D1417 Fedders logo T874D1165

D1425 Climatrol logo T874D1165

D1433 Singer logo; no. 02005785; 8°F (4.4°C) differential

T874D1165 between H1 and H2

D1441 American Air Filter T874D1165

D1474 Carrier; no. HH07AT072-03; Celsius scale T874D1165

T872E 2-stage cool

E1002 Standard OEM T874E1016

E1010 TRADELINE T874E1016

E1028 Westinghouse logo T874E1016

When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.

33 60-2485—8

Page 34

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 6. T872-T874 Thermostat Cross Reference.

Model Number Description

T874 Trade

Replacement

E1036 American Standard logo T874E1016

E1044 York logo; locking cover T874E1016

E1051 ITT logo T874E1016

E1069 Climatrol logo T874E1016

E1077 Airtemp (Chrysler) logo T874E1016

E1085 Lennox logo T874E1016

E1093 Trane logo T874E1016

E1101 Dunham-Bush logo T874E1016

E1119 Fedders logo T874E1016

E1127 Climatrol logo T874E1016

E1135 General Electric logo; no. AY28X108 T874E1016

E1143 Lennox logo; Celsius scale T874E1016

E1150 Celsius scale T874E1016

E1168 Airtemp logo T874E1016

T872F 2-stage heat

F1001 Standard OEM T874F1015

F1019 TRADELINE T874F1015

F1027 Lennox logo; fast cycle heat anticipator T874C1018

F1035 Luxaire logo; fast cycle performance on both heat

stages.

T874C1018 M839 draws 0.72A; set adjustable

heat anticipator to setting of 0.9A for proper cycle rate.

F1043 York logo; locking cover; used with M839. T874C1018

F1050 Raehco logo T874F1015

F1068 Fast cycle performance on both heat stages. T874C1018

F1076 Wesco logo T874F1015

F1084 Lennox logo T874F1015

F1092 Auto Gas logo T874F1015

F1100 Celsius scale T874F1015

F1118 Lennox logo; Celsius scale T874F1015

F1126 Stages 1 and 2 heat electrically isolated; used with

None

Q672D1002

F1134 Square D logo; HCD-4 T874F1015

F1159 Wesco logo; heat anticipator set at 0.8A T874F1015

F1167 York logo T874F1015

F1175 Oneida Heater logo; no. 30A0287-01; used with

Q672K1012.

T874F1015/ Q674K1026

T872G Heat pump models; 2-stage heat,

1-stage cool, 1-stage changeover.

G1000 Fast cycle performance stage 2 heat; fixed

anticipator stage 1 heat and cool; changeover with

Y594G1252 Wiring differences (old=new):

W=W2, X1=X.

cooling; used with Q672F1018.

G1018 Adjustable anticipator stage 2 heat; fixed

anticipator stage 1 heat and cool; changeover with

Y594G1393 Wiring differences (old=new):

Y1=O, Y2=Y.

cooling; used with Q672E1027.

When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.

Remarks

60-2485—8 34

Page 35

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 6. T872-T874 Thermostat Cross Reference.

Model Number Description

G1026 Lennox logo; fast cycle performance; stage 2 heat;

fixed anticipator stage 1 heat and cool;

T874 Trade

Replacement

None See subbase description for

Remarks

replacement information. changeover with cooling; used with Q672E1019, F1067.

G1034 Westinghouse logo; adjustable anticipator stage 2

heat; fixed anticipator stage 1 heat and cool;

Y594G1252 Wiring differences (old=new):

W=W2. changeover with cooling; used with Q672F1091, F1141, F1257 or Q672J1013, J1062.

G1042 York logo; fixed anticipator on all stages heat and

Y594G1567 cool; changeover with cooling; used with Q672J1021.

G1059 TRADELINE; no anticipator stage 2 heat; fixed

anticipator stage 1 heat and cool; changeover with

Y594G1161 Designed for use on General

Electric heat pumps.

cooling; used with Q672J1039 outdoor reset.

G1067 Lennox logo; no. P-8-11222; fast cycle

performance; stage 2 heat; fixed anticipator stage

See subbase description for

replacement information. 1 heat and cool; changeover with cooling; used with Q672E1142, F1083.

G1075 Carrier logo; adjustable anticipator stage 2 heat;

fixed anticipator stage 1 heat and cool;

See subbase description for

replacement information. changeover with cooling; used with Q672J1054, L1052.

G1083 Adjustable anticipator stage 2 heat; fixed

Y594G1252 anticipator stage 1 heat and cool; changeover with cooling; includes shunt to bypass stage 2 anticipator with auxiliary heat relays; used with Q672F1158.

G1091 Lennox logo; same as T872G1026 except meets

DoD specs.

G1109 Tappan logo; no. 080-13708-52; adjustable

Y594G1252 Wiring differences (old=new): C=X.

See subbase description for replacement information.

anticipator stage 1 heat and cool; changeover with cooling; used with Q672F1117.

G1117 Changeover; used with Q672F1125. Y594G1252 Wiring differences (old=new): C=X.

G1125 Lennox logo; no. 63A0401; Celsius scale; isolated

None auxiliary heat power circuit; fast cycle anticipator stage 2 heat.

G1133 Rheem logo; no. RXMT-B71; adjustable

Y594G1252 anticipator stage 2 heat; fixed anticipator stage 1 heat and cool; changeover with cooling; includes shunt to bypass stage 2 anticipator with auxiliary heat relays; used with Q672F1158, F1232.

G1141 Ruud logo; adjustable anticipator stage 2 heat;

Y594G1252 fixed anticipator stage 1 heat and cool; changeover with cooling; includes shunt to bypass stage 2 anticipator with auxiliary heat relays; used with Q672F1158.

G1158 Carrier logo; same as T872G1075. Except DoD

styling.

See subbase description for

replacement information.

G1166 BDP used with Q672F1125. Y594G1252 Wiring differences (old=new): C=X.

G1174 BDP used with Q672F1125. Y594G1252 Wiring differences (old=new): C=X.

G1182 Carrier; no. HH07AT071C; Celsius scale; used

with Q672L1052, J1054.

G1190 Tappan; no. B13708-57; used with Q672L1078 for

See subbase description for

replacement information.

None 8 and 10 ton heat pumps with 2 compressors.

When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.

35 60-2485—8

Page 36

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 6. T872-T874 Thermostat Cross Reference.

Model Number Description

G1208 Marvair logo; special for Crispaire; used with

T874 Trade

Replacement

Y594G1393

Remarks

Q672F1166, F1323.

G1216 Janitrol logo; no. 26G05; stage 2 heat anticipator

Y594G1252 Wiring differences (old=new): C=X.

set at 1.2A; used with Q672F1117.

G1224 TRADELINE; adjustable anticipator stage 2 heat;

Y594G1419 fixed anticipator stage 1 heat and cool; changeover in cool; used with Q672F1208.

G1232 Heat Wave (Southwest Mfg.) logo; stage 2 heat

anticipator set at 1.2A; used with Q672F1224.

G1240 Lennox; fast cycle anticipator stage 2 heat; used

None with Q672F1240.

G1257 Carrier logo; no. HH07AT073; used with

None Q672L1169 (HH93AZ071).

G1265 Addison logo; used with Q672F1265. Y594G1252 Wiring differences (old=new): C=X.

G1273 Carrier logo; (DoD model); 68°F (20°C) maximum

heating; 78°F (26°C) minimum cooling; used with

See subbase description for replacement information.

Q672L1052, J1054

G1281 Wesco logo; used with Q672F1265. Y594G1252 Wiring differences (old=new): C=X.

G1299 York logo; meets DoD specs; used with

Y594G1567 Q672L1177.

G1307 Carrier; no. 38EQ1900; Celsius; used with

Q672J1054, L1052.

G1315 Luxaire special; stage 2 heat anticipator set to

Y594G1252

See subbase description for replacement information.

1.2A; used with Q672F1281.

G1323 Lennox special; used with Q672L1201 and

None C815A1013.

G1331 York; used with Q672J1021. Y594G1567 Wiring differences (old=new):

X=X1, L=X2, W=E; Y1-W1 and Y2W2 jumpers required.

G1356 Westinghouse; used with Q672L1219. T874D1165/

Q674F1022

Wiring differences (old=new): X=X1, L=X2, W=E; Y1-W1 and Y2W2 jumpers required.

G1364 York; used with Q672D1077. None

G1372 Tappan/Janitrol logo; no. B-13708-521;

Y594G1252 Wiring differences (old=new): C=X. used with Q672F1117.

G1398 York logo; no. 025-21454C; used with Q672J1021. Y594G1567

T872H Heat pump model; 1 stage heat,

1 stage cool, 1 stage changeover.

H1009 Command-Aire logo; fixed anticipator stage 1 heat

Y594H1012 and cool; changeover with cooling; used with Q672C1086.

H1017 Friedrich logo. Y594H1012

H1025 Friedrich logo; Celsius. Y594H1012

T872M 1 stage heat, 1 stage cool with stage 2 heat factory

set at 60°F (16°C).

M1003 Standard OEM; used with Q672D and external

switching means.

T874C1125 T874C1125 has 12°F (6.7°C)

differential between stage 1 and stage 2 heat.

T872N Heat pump model; 2-stage heat, 1-stage cool plus

changeover, changeover in heat mode.

N1002 None

When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.

60-2485—8 36

Page 37

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 6. T872-T874 Thermostat Cross Reference.

Model Number Description

N1010 Williamson logo; adjustable anticipator stage 1 and

2 heat; fixed anticipator stage 1 cool; used with

T874 Trade

Replacement

T874N1016/ Q674F1220

Remarks

Q672F1133 or F1315.

N1028 TRADELINE heat mode changeover; used with

T874N1016

Q672F1216.

N1036 Bard; used with Q672F1299. T874N1016/

Q674F1220

N1044 Thermotron logo; 1st stage changeover heat

mode; used with Q672F1299.

T874N1016/ Q674F1220

T872Q 1-stage heat; used with another T872 for heating

setback.

Q1009 Standard OEM T874C1125

Q1017 York logo T874C1125 Replacement only good for

1-stage heat and 1-stage cool applications.

Q1025 ITT logo None

Q1033 Lennox logo; no. P-8-8899. None

Q1041 Lennox logo; no. 63A6401. None

T872R Heat pump model; 2-stage heat, 1-stage cool,

manual changeover.

R1008 Fixed anticipator stage 1 heat and cool; no

anticipator stage 2 heat; changeover with cooling;

Y594R1425 Wiring differences (old=new):

W=W2; W1-Y1 jumper required.

used with Q672B1046.

R1016 Addison same as T872R1008; used with

Q672B1103.

R1024 Lennox logo; fast cycle stage 2 heat; fixed

anticipator stage 1 heat and cool; changeover with

Y594R1425 Wiring differences (old=new):

W=W2; W1-Y1 jumper required.

See subbase description for replacement information.

cooling; used with Q672B1160 and Q672L1003.

R1032 York logo; fixed anticipator stage 1 and 2 heat and

Y594R1664 stage 1 cool; changeover with cooling; used with Q672L1011.

R1040 Lennox logo; fast cycle stage 2 heat; fixed

anticipator stage 1 heat and cool; isolated stage 2

See subbase description for

replacement information. heat switch; changeover with cooling; used with Q672B1202 no. P-8-11221, Q672L1029

R1057 TRADELINE; fixed anticipator stage 1 heat and

cool; no anticipator stage 2 heat; changeover on cooling; used with Q672L1037; outdoor reset.

R1065 Adjustable anticipator stage 2 heat; fixed

Y594R1763 Designed for use on General

Electric heat pumps. Wiring

differences (old=new): A=T.

Y594R1243 anticipator stage 1 heat and cool; changeover on cooling; used with Q672L1045.

R1073 Lennox logo; no. 63A0301; Celsius scale;

None separate auxiliary heat power circuit; fast cycle stage 2 heat antic.

R1081 Ruud logo; same circuit as T872R1065; used with

Y594R1243 Q672L1045, L1136.

R1099 Dunham Bush special; used with Q672L1060,

Y594R1243 L1383.

R1107 Rheem; no. RXMT-B70; used with Q672L1045,

Y594R1243 L1136.

R1115 Friedrich logo; fixed anticipator; used with

Q672B1244, L1086.

When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.

See subbase description for replacement information.

37 60-2485—8

Page 38

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 6. T872-T874 Thermostat Cross Reference.

Model Number Description

T874 Trade

Replacement

Remarks

R1123 York logo; no. 025-21453C; Celsius scale. Y594R1664

R1131 Lennox logo; separate auxiliary heat power circuit;

None fast cycle stage 2 heat anticipator; outdoor reset; used with Q672L1144, C815A1013.

R1149 Westinghouse logo; adjustable stage 2 heat

anticipator; cooling changeover; fixed anticipator

Y594R1243 Wiring differences (old=new):

W=W2. stage 1 heat and cool; used with Q672L1110, L1128, L1151.

R1156 Marvair logo; used with Q672L1094, L1250. Y594R1243 Replacement has auto fan in

Emergency Heat mode.

R1164 Bard; used with Q672L1185. Y594R1243

R1172 Heil Quaker; used with Q672L1193. Y594R1243 Wiring differences (old=new): B=X,

W=W2.

R1180 York; Celsius; used with Q672L1011. Y594R1664

R1198 TRADELINE; used with Q672L1227 Y594R1243

R1206 For use with W89; used with Q672L1235. None

R1214 Intertherm logo; used with Q672L1276. Y594R1300 Wiring differences (old=new):

W1=B, Z=L, K=E.

R1222 York logo; used with C815A1039; adjustable

Y594R1672

anticipator stage-2 heat; used with Q672L1284

R1230 Amana logo; no. C62397-1; used with

None

Q672L1300, W89.

R1255 Singer logo; used with Q672L1326 and W89. None

R1271 Westinghouse logo; used with Q672L1375 and

Y594R1664

W89.

R1297 York; Celsius scale; used with Q672L1011. None

R1305 Used with Q672L1235 and W89. None

R1321 Duotherm logo; used with Q672L1409, and W89. None

R1339 Williamson; used with Q672L1391. Y594R1243

T872S Heat pump model; 2-stage heat plus changeover,

1-stage cool.

S1005 Westinghouse logo; adjustable anticipator stage 1

and 2 heat; fixed anticipator stage 1 heat; changeover with heating: used with Q672C1045

T874C1018/ Q674C1058

Wiring differences (old=new):

V=RC-RH, F=G, C=Y1, Z=B,

H2=W2; W1-Y1 jumper required.

T872T 1-heat stage, 1-vent and 2-cool stages.

T1004 Trane logo; used with Q672B1129. None

T872W 3-heat stages, 2-cool stages, manual changeover

W1019 Lennox logo; no. 52C7501; used with Q672L1342

None

and C815A1013.

W1027 Westinghouse logo; used with Q672L1268 and

None

C815A1021.

W1035 TRADELINE; used with C815A1043 and

Y594W1014

Q672B1251.

When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.

60-2485—8 38

Page 39

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 7. Q672-Q674 Subbase Cross Reference.

Model Number Description

Q674 Trade

Replacement

Remarks

Q672A System: HEAT-AUTO-COOL, Fan: AUTO-ON

A1005 Standard OEM Q674A1019

A1013 TRADELINE Q674A1019

A1021 RC-RH jumper Q674A1019 RC-RH jumper required.

A1039 RC-RH jumper; Chek Lite Q674A1019 RC-RH jumper required.

Q672B System: HEAT-OFF-COOL, Fan: AUTO-ON

B1004 Standard OEM Q674B1034

B1012 Isolated G terminal. Q674B1018

B1020 System: HEAT-OFF-RESET-COOL Q674B1034 Used system off as reset position.

B1038 TRADELINE Q674B1034

B1046 Heat pump circuit; used with T872R1008. Y594R1425 Wiring differences (old=new):

W1=Y1, W=W2.

B1053 RC-RH jumper Q674B1034 RC-RH jumper required.

B1061 Chek Lite Q674B1034

B1079 Auto fan operation in heat and cool. Q674B1075

B1087 Carrier no. HH93AZ078; RC-RH jumper. Q674B1075

B1095 Carrier no. HH93AZ084; RC-RH jumper. Q674B1034

B1103 Addison; heat pump circuit; used with

T872R1016.

Y594R1425 Wiring differences (old=new):

W=W2; W1-Y1 jumper required.

B1111 Carrier no. HH93AZ080; isolated G terminal. Q674B1018

B1129 Trane special circuit; used with T872T1004. None

B1137 RC-RH jumper; isolated G terminal. Q674B1018 RC-RH jumper required.

B1145 Fedders special Q674B1034 RC-RH jumper required.

B1152 Fedders special; auto fan operation in heat

Q674B1075

and cool.

B1160 Lennox; heat pump circuit; used with

T872R1024; includes compressor lockout in

Y594R1243 Wiring differences (old=new):

V-VR=R, M=Y, Y=W2, F=G, R=O.

EM. HT.

B1178 General Electric no. AY28X107; auto fan

Q674B1075

operation in heat and cool.

B1186 Trane; isolated G terminal; Filter LED. Q674B1018

B1194 General Electric no. AY28X124; auto fan

operation in heat and cool.

Q674B1075 Set T874 stage-1 anticipator for

combined load of heat relay and fan relay.

B1202 Lennox no. P-8-11223; heat pump circuit; used

with T872R1040.

Y594R1243 Wiring differences (old=new):

V-VR=R, M=Y, Y=W2, F=G, R=O.

B1210 None

B1228 General Electric no. BAY28X137; isolated

Q674B1018

G terminal.

B1236 Carrier no. HH-93AZ079; RC-RH jumper;

LOCKOUT LED indicates compressor lockout

Q674B1034 RC-RH jumper; LED cannot be

provided in TRADELINE model.

switch activated.

B1244 Friedrich; heat mode changeover; used with

T872R1115.

T874C1018/ Q674B1034

Wiring differences (old=new): C=no connection; RC-RH and W1-Y1 jumpers required.

B1251 Used with T872W1035 and C815A1043. Y594W1014

When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase.

39 60-2485—8

Page 40

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 7. Q672-Q674 Subbase Cross Reference.

Model Number Description

B1269 Whalen; Hi-Lo fan switch; constant fan in heat

Q674 Trade

Replacement

None

Remarks

and cool system switch positions; used with T872C1574.

B1277 Square D no. HCB-5. Q674B1034

B1285 Wards; RC-RH and F-W3 jumpers; used with

T872C1673.

Gas Furnace: T874C1018/ Q674B1034

Electric Furnace: T874C1018/

Adjust anticipator faster for correct performance.

Q674B1075

B1293 Lennox no. 41C96; used with T872C1673. Same as

Q672B1285

Q672C System: OFF-AUTO, Fan: AUTO-ON

C1003 Standard OEM Q674C1058

C1011 Westinghouse; RC-RH jumper. Q674C1058 RC-RH jumper required.

C1029 W1-Y2 jumper; for heat pump; used with

T872D1136.

Q674E1049 Replacement has heat/cool system

switching.

C1037 Chrysler Airtemp; System: COOL-OFF-AUTO. Q674C1058

C1045 Westinghouse; heat pump; used with

T872S1005.

T874C1018/ Q674C1058

Wiring differences (old=new): V=RC-RH, F=G, C=Y1, Z=B, H2=W2; W1-Y1 jumper required.

C1052 Isolated stage 2 heat circuit for dc electric heat

relay.

Recontrol Use T874G1246/Q674F1212 which

adds HEAT-COOL-EM.HT. system switch.

C1060 Fedders special. Q674C1058

C1078 General Electric no. AY28X109. Q674C1058

C1086 Command-Aire; heat pump; used with

Y594H1012

T872H1009.

C1102 TRADELINE Q674C1058

Q672D System: None. Fan: None.

D1002 Standard OEM; used with T872F1126. Q674D1040

D1010 Lennox special. None

D1028 Carrier; RC-RH jumper. None

D1036 Carrier no. HH93AZ070; RC-RH jumper. Q674D1040 RC-RH jumper required.

D1044 General Electric no. AY-28X100. None

D1069 Square D no. HCB-4. None

D1077 York; used with T872G1364. None

D1085 TRADELINE Q674D1040

Q672E System: OFF-HEAT-AUTO-COOL

Fan: AUTO-ON

E1001 Standard OEM Q674E1049

E1019 Lennox no. P-8-8892; heat pump; cool mode

changeover; used with T872G1026.

E1027 Heat pump circuit; W1-Y2 jumper; cool mode

changeover; used with T872G1018.

E1035 Heat pump circuit; W1-Y2 jumper; cool mode

changeover.

T874D1165/ Q674B1075

Y594G1393 Wiring differences (old=new): Y1=O,

Y2=Y.

Y594G1393 Wiring differences (old=new): Y1=O,

Y2=Y.

E1043 Heat pump circuit; heat mode changeover. Q674E1049 Wiring differences (old=new):

W1=B, W2=W1; W1-Y1 jumper.

When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase.

60-2485—8 40

Page 41

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 7. Q672-Q674 Subbase Cross Reference.

Model Number Description

Q674 Trade

Replacement

Remarks

E1050 TRADELINE Q674E1049

E1068 RC-RH jumper; used with T872C1699. Q674E1049 RC-RH jumper required.

E1076 RC-RH internal jumper; EM. HT. LED. Q674E1049 RC-RH jumper required.

E1084 Carrier no. HH93AZ076; RC-RH jumper. Q674E1049 RC-RH jumper required.

E1092 Carrier no. HH93AZ082; RC-RH jumper; B

Q674E1049

terminal; isolated G terminal.

E1100 General Electric no. AY28X099. Q674E1049

E1118 Airtemp; heat pump; used with T872D1169. T874D1165/

Q674E1049

Wiring differences (old=new): A=W1; set H1 anticipator to 1.2A.

E1126 Common R terminal. Q674E1049 RC-RH jumper required.

E1134 ITT Nesbitt; RC-RH jumper; O and B terminals;

Q674E1049

isolated G terminal.

E1142 Lennox no. P-8-11224; heat pump;

V-VR jumper; cool mode changeover; used with

Y594G1252 Wiring differences (old=new):

V-VR=R, Y=W2, R=O, M=Y, F=G.

T872G1067.

E1159 Carrier no. HH93AZ077; RC-RH jumper;

LOCKOUT LED indicates activation of

Q674E1049 RC-RH jumper required; no LED in

TRADELINE model.

compressor lockout switch.

E1167 Square D no. HCB-2; Chek Lite. Q674E1049

E1183 Square D no. HCB-3. Q674E1049

E1191 Lennox; HIGH and LOW LEDs; used with

Q674E1049 No LEDs on replacement.

T872D1045.

Q672F System: EM. HT.-HEAT-AUTO-COOL-OFF

Fan: AUTO-ON.

F1000 With EM. HT. LED; used with T872C1699. Q674F1022 Remove W3-X2 jumper to E-X2.

F1018 Heat pump; heat mode changeover; Chek Lite;

used with T872G1000.

Y594G1252 Wiring differences (old=new):

W=W2, X1=X.

F1026 Chek Lite; W2-X2 jumper. Q674F1022

F1034 Airtemp; EM. HT. LED; RC-RH and X2-E

jumpers.

Q674F1022 If RC-RH jumper removed on

Q672F1034, Q674F1022 does not replace.

F1042 W2-X2 jumper; Chek Lite. Q674F1022

F1059 Carrier no. HH93AZ074; EM. HT. LED. Q674F1022 Remove W2-X2 jumper to E-X2; X

terminal same as C.

F1067 Lennox; heat pump; cool mode changeover;

None

EM. HT. LED; used with T872G1026.

F1075 Heat pump circuit; EM. HT. LED; 2 terminal; RC-

None

RH jumper.

F1083 Lennox no. P-8-11225; heat pump;

None V-VR jumper; cool mode changeover; EM. HT. LED; used with T872G1067.

F1091 Westinghouse; heat pump; EM. HT. LED; cool

mode changeover; compressor lockout in

Y594G1252 Wiring differences (old=new):

W=W2.

EM. HT.; used with T872G1034.

F1109 Airtemp no. 3778567ACC; R-X2 jumper;

Q674F1022 R-X2 jumper required. EM. HT. LED.

F1117 Tappan no. 080-13708-53; heat pump; EM. HT.

Y594G1252 Wiring differences (old=new): C=X. LED; cool mode changeover; compressor lockout and auto fan in EM. HT.; used with T872G1109, G1216, G1372.

When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase.

41 60-2485—8

Page 42

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 7. Q672-Q674 Subbase Cross Reference.

Model Number Description

F1125 BDP no. 3442DP90; used with T872G1117,

Q674 Trade

Replacement

Y594G1252 Wiring differences (old=new): C=X.

G1166, G1174.

F1133 Williamson; heat pump; EM. HT. LED; heat

mode changeover; compressor lockout in

T874N1016/ Q674F1220

EM. HT.; used with T872N1010.

F1141 Westinghouse; EM. HT. LED; auto fan in

EM. HT.; used with T872G1034.

F1158 Rheem Ruud; heat pump; EM. HT. LED; cool

Y594G1252 Wiring differences (old=new):

W=W2.

Y594G1252 mode changeover; compressor lockout in EM. HT.; used with T872G1083, G1133, G1141; auto fan in EM. HT.

F1166 Crispaire; EM. HT. LED; used with T872G1208. Y594G1252

F1174 Carrier no. HH93AZ081; EM. HT. LED. Q674F1022

F1182 Square D no. HCB-1; Chek Lite; R-X2 jumper;

System: Aux. Heat replaces EM. HT.

Q674F1022 R-X2 jumper; add monitor switch

between X1 and low side of power.

F1190 EM. HT. LED; X2-E and RC-RH jumpers. None

F1208 TRADELINE; cool mode changeover; EM. HT.

Y594G1419 LED; used with T872G1224.

F1216 TRADELINE; heat mode changeover; EM. HT.

LED; used with T872N1028.

F1224 Heatwave (Southwest Mfg.); compressor

T874N1016/

Q674F1220

Y594G1252 lockout in EM. HT.; EM. HT. LED; used with T872G1232.

F1232 Rheem; cool mode changeover; EM. HT. and

Y594G1252 AUX. HEAT LEDs; compressor lockout in EM. HT.; used with T872G1133.

F1240 Lennox; cool mode changeover; EM. HT. and

None SERVICE LEDs; used with T872G1240.

F1257 Westinghouse; cool mode changeover;

EM. HT. and AUX. HEAT LEDs; auto fan in

Y594G1252 Wiring differences (old=new):

W=W2.

EM. HT; used with T872G1034.

F1265 Wesco Addison; Chek and EM. HT. LEDs; used

Y594G1252 Wiring differences (old=new): C=X. with T872G1281, G1265.

F1273 Southwest special; no. 0361-136; W2-X2

None jumper.

F1281 Luxaire special; used with T872G1315. Y594G1252

F1299 Bard special; used with T872N1036, N1044. T874N1016/

Q674F1220

F1315 Williamson special; used with T872N1010. T874N1016/

Q674F1220

F1323 Crispaire special; used with T872G1208. Y594G1252

Q672G System: OFF-AUTO. Fan: None.

G1009 Standard OEM Q674G1070

G1017 Singer; O-B jumper; used with T872D1375. Q674G1070

G1025 Includes O and B terminals. Q674G1070

G1033 General Electric no. AY28X102. Q674G1070

G1041 Singer no. 02005649; French wording; O-B

Q674G1070 Less French wording. jumper.

G1066 SLI-Mammoth; heat pump; heat mode

changeover.

When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase.

Q674G1070 Connect fan (G) wire to Y1 terminal;

B-O and RC-RH jumpers.

Remarks

60-2485—8 42

Page 43

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 7. Q672-Q674 Subbase Cross Reference.

Model Number Description

G1074 Singer no. 02005754; X1 and X2 terminals for

Q674 Trade

Replacement

None

Remarks

field-added indicator lights; used with T872D1375.

G1082 Singer no. 02005792; X1 and X2 terminals for

None field-added indicator lights; used with T872D1375.

G1090 TRADELINE; B and O terminals. Q674G1070

Q672H System: OFF-ON

Fan: NIGHT INT.-DAY CONT.

H1008 Used with T872. None

Q672J System: EM. HT.-AUTO-OFF

Fan: AUTO-ON.

J1005 With EM. HT. LED; used with T872C or D. None

J1013 Westinghouse; heat pump; EM. HT. LED; cool

Y594G1252 mode changeover; compressor lockout in EM. HT.; used with T872G1034.

J1021 York; heat pump; EM. HT. LED; cool mode

Y594G1567 changeover; compressor lockout and auto fan in EM. HT.; E-W jumper; used with T872G1042, G1331, G1398.

J1039 Heat pump; EM. HT. and AUX. HEAT LEDs;

cool mode changeover; compressor lockout and

Y594G1161 Designed for use on General

Electric heat pumps.

auto fan in EM. HT.; used with T872G1059.

J1047 Singer no. 02005699; heat pump; EM. HT. LED;

Q674F1022 heat mode changeover.

J1054 Carrier no. HH93AZ073A; heat pump; EM. HT.

Y594G1252 Wiring differences (old=new): C=X. LED; cool mode changeover; compressor lockout in EM. HT.; used with T872G1075, G1182, G1307.

J1062 Westinghouse; EM. HT. and AUX. HEAT LEDs;

used with T872G1034.

Y594G1252 Wiring differences (old=new):

W=W2.

Q672K System: OFF-HEAT-AUTO-COOL. Fan: None.

K1004 Carrier no. HH93AZ072. Q674E1049 Fan switch does not function.

K1012 Oneida Heater no. 30A0288-01; System: OFF-

WOOD-WOOD/OIL-OIL; used with T872F1175.

T874F1155/

Q674K1026

Q672L System: EM. HT.-HEAT-OFF-COOL.

Fan: ON-AUTO.

L1003 Lennox; heat pump; EM. HT. LED; cool mode

Y594R1425 changeover; used with T872R1024.

L1011 York; heat pump; EM. HT. LED; cool mode

Y594R1664 changeover; compressor lockout and auto fan in EM. HT.; used with T872R1032, R1180, R1297.

L1029 Lennox no. P-8-11226; heat pump; EM. HT.

LED; V-VR jumper; cool mode changeover;

Y594R1425 Wiring differences (old=new):

V-VR=R, M=Y, Y=W2, F=G, R=O. compressor lockout in EM. HT.; used with T872R1040.

L1037 Heat pump; EM. HT. and AUX. HT. LEDs; cool

mode changeover; compressor lockout and auto fan in EM. HT.; used with T872R1057.

L1045 Rheem; heat pump; EM. HT. LED; cool mode

Y594R1763 Wiring differences (old=new): A=T;

designed for used on General

Electric heat pumps.

Y594R1243 changeover; compressor lockout in EM. HT.; auto fan in EM. HT; used with T872R1065, R1081, R1107.

When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase.

43 60-2485—8

Page 44

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 7. Q672-Q674 Subbase Cross Reference.

Model Number Description

L1052 Carrier no. HH93AZ075; heat pump; EM. HT.

Q674 Trade

Replacement

Y594R1615 Wiring differences (old=new): C=X.

Remarks

LED; cool mode changeover; compressor lockout in EM. HT.; used with T872G1075, G1182, G1273, G1307.

L1060 Dunham Bush; EM. HT. LED; used with

Y594R1243

T872R1099.

L1078 Tappan no. B13708-58; heat pump; EM. HT.

None LED; cool mode changeover; compressor lockout in EM. HT.; EM. HT. relay provides fan operation in EM. HT.; used with T872G1190.

L1086 Friedrich; heat mode changeover; EM. HT. LED;

used T872R1115 with L terminal.

L1094 Crispaire; W2-H jumper; EM. HT. LED; used

with T872R1065, R1156.

L1102 Fedders; heat mode changeover; EM. HT. LED;

used with T872C1509, C1517, C1541.

L1110 Westinghouse; EM. HT. LED; used with

T872R1149.

L1128 Westinghouse; EM. HT. LED; used with

T872R1149.

L1136 Rheem no. 41-20796-07; cool mode

Y594R1243 Wiring differences (old=new): X2=E,

C=X.

Y594R1243 Replacement has auto fan in

Emergency Heat mode.

Y594R1425 Wiring differences (old=new): K=E,

C=X; remove Y-W1 jumper.

Y594R1243 Wiring differences (old=new):

W=W2.

Y594R1243 Wiring differences (old=new):

W=W2.

Y594R1243 changeover; EM. HT. and AUX. HT. LEDs; used with T872R1081, T872R1107.

L1144 Lennox; V-VR jumper; EM. HT. and SERVICE

None LEDs; isolated stage 2 heat; used with T872R1131, C815A1013.

L1151 Westinghouse; AUX. HT. and EM. HT. LEDs;

used with T872R1149.

L1169 Carrier no. HH93AZ071; EM. HT. LED; used

Y594R1243 Wiring differences (old=new):

W=W2.

None with T872G1257 (HH07AT073).

L1177 York; DoD; EM. HT. LED; used with T872G1299. Y594G1567

L1185 Bard; used with T872R1164. Y594R1243

L1193 Heil Quaker no. NAXA001TS01; used with

T872R1172.

L1201 Lennox special; no. 1485701; used with

Y594R1243 Wiring differences (old=new): B=X,

W=W2.

None T872G1323.

L1219 Westinghouse special; used with T872G1356. T874D1165/

Q674F1022

Wiring differences (old=new): X=X1, L=X2, W=E; Y1-W1 and Y2-W2 jumpers required.

L1227 Heat pump; used with T872R1198. Y594R1243

L1235 Intertherm; used with T872R1206, R1305. None

L1250 Crispaire special; used with T872R1156 and

Y594R1243 C815A1021.

L1268 Westinghouse special; used with T872W1027

None and C815A1021.

L1276 Intertherm special; used with T872R1214. Y594R1300 Wiring differences (old=new):

W1=B, Z=L, K=E.

L1284 York special; used with T872R1222. Y594R1672

L1300 Amana special; no. C62345-1; used with

None T872R1230.

L1326 Singer; used with T872R1255. None

When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase.

60-2485—8 44

Page 45

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 7. Q672-Q674 Subbase Cross Reference.

Model Number Description

L1342 Lennox no. 52C7601; used with T872W1019

Q674 Trade

Replacement

None

and C815A1013.

L1375 Westinghouse; used with T872R1271, W89. None

L1383 Dunham Bush; used with T872R1099. Y594R1243

L1391 Williamson; used with T872R1339. Y594R1243

L1409 Duotherm special; used with T872R1321, W89. None

Q672N System: OFF-HEAT-COOL-EVAP.

N1001 Goettl; heat pump; heat mode changeover;

None evaporative cooler circuit; Fan: AUTO-ON; System: AUTO; used with T872C1459.

N1019 Goettl; heat pump; heat mode changeover;

None evaporative cooler circuit; W1-Y1 jumper; used with T872C1459.

N1027 Siegler special; used with T872C1707. None

Q672P System: EM. HT.-HEAT-COOL.

P1009 Carrier special; no. HH93AZ069; used with

T872G1075 (HH07AT071).

When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase.

Y594R1243 Replacement has OFF system

switch position

Remarks

45 60-2485—8

Page 46

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 8. T874 Cross Reference.

Model

Number

Fig.

No. Description

Trade Model

Replacement Remarks

T874A 1-stage heat, 1-stage cool.

A1002 44, 65 Honeywell logo; Standard OEM; used with Q674B1331. T874A1036

A1010 44 Honeywell logo; includes Allen wrench and screws to

T874A1010 lock cover; non-adjustable range stops set at 72°F (max. heat) and 78°F (min. cool) (22-26°C); field adjustable locking levers.

A1028 44 Honeywell logo; heat anticipator factory set at 0.4A. T874A1036

A1036 44 Honeywell logo; TRADELINE® model; includes Allen

T874A1036 wrench and screws to lock cover; field adjustable locking levers.

A1044 44 Obsolete

3006C; °F/°C scaleplate.

A1051 44 Lennox logo; part no. 12F9901; °F/°C scaleplate; heat

anticipator set at 0.45A.

A1069 44 Obsolete

A1077 46, 82 Obsolete. Amana Air Conditioning logo; part no.

. AAF/Snyder General logo; part no. 4ELN-

T874A1036 Replacement has °F

. Westinghouse logo; used with Q674A-E,G. T874A1036

T874A1036

scaleplate.

D68535-1; heat anticipator factory set at 1.2A; used with Q674B1075, E1056; used in Y594A1001, A1019.

A1085 44, 46,

55, 66

A1093 44 Obsolete

A1101 51, 53 Carrier logo; part no. HH07AT174; used with Q674B. Y594C1421 or

Obsolete

. Trane logo; part no. 13510451; used with

Q674B1018, B1075, D1008.

. McQuay logo; part no. 02005935; °F/°C

scaleplate.

T874A1036

T874A1036 Replacement has °F/°C

scaleplate.

When using the T874C1036,

T874A1036

set stage 1 heat anticipator for total current draw of fan and stage 1 heat primary.

A1119 82 Obsolete

°C scaleplate; used with Q674E1007; used in

. Sears logo; part no. 541. 91441/49. 9144; °F/

T874A1036 Replacement has °F

scaleplate.

Y594A1068.

A1127 44 Obsolete

. Climate Control logo; part no. 02005936; °C

scaleplate.

A1135 44 Fedders multi-logo; part no. THTX-110-WCHA,

T874A1036 Replacement has °F

scaleplate.

T874A1036 88-58-00500-001.

A1143 44 Honeywell logo; °C scaleplate. T874A1036 Replacement has °F

scaleplate.

A1150 44 Honeywell logo; TRADELINE model; includes Allen

T874A1150 wrench and screws to lock cover; field adjustable locking levers (68°F max. heat, 78°F min. cool).

A1168 44 Obsolete

A1176 44 Honeywell logo; meets DoD specs; includes Allen

. Trane Comfort Corps logo. T874A1036

T874A1176 wrench and screws to lock cover; no thermometer; nonadjustable range stops set at 72°F (max. heat) and 78°F (min. cool) (22-26°C); field adjustable locking levers.

A1184 51, 53 Trane logo; part no. BAY28X182; °F/°C scaleplate;

automatic fan in heating and cooling modes; heat anticipator set at 0.4A; used with Q674B1141, E1080.

T874A1036

When used with Q674E1080, set stage 1 heat anticipator for total current draw of fan and stage 1 heat primary; replacement has °F scaleplate.

A1192 44 Obsolete

heat anticipator factory set at .458A.

Both the thermostat and subbase must be replaced.

. Lennox logo; part no. 13F0001; °C scaleplate;

T874A1036 Replacement has °F

scaleplate.

60-2485—8 46

Page 47

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 8. T874 Cross Reference.

Model

Number

A1200 51, 53 Obsolete. Carrier logo; part no. HH07AT164; °C

Fig.

No. Description

Trade Model

Replacement Remarks

T874A1036 scaleplate; includes Allen wrench and screws to lock cover; used with Q674B.

A1226 44 Honeywell logo; Honeywell Canada TRADELINE model;

T874A1036 Replacement has °F °C scaleplate; includes Allen wrench and screws to lock cover.

A1234 44 Obsolete. Friedrich Climate Master logo; heat anticipator

T874A1036 factory set 1.2A.

A1242 44 Obsolete

. Friedrich Climate Master logo. T874A1036

A1259 44 Obsolete. Wesco logo; heat anticipator set at 0.8A. T874A1036

A1267 59 Obsolete

A1275 44 Obsolete

. McQuay logo; used with Q674Q1004. T874A1036

. Lennox logo; part no. 13F0101; meets DoD

T874A1176 specifications.

A1283 75 McQuay Air Conditioning logo; part no. 03005047; used

T874A1036 Replacement does not have with Q674C1132 and thermistor to display outdoor temperature.

A1291 64 No logo; three-speed fan; one setpoint lever for heat and

cool setpoints; used with Q674Q1012; used in

T874A1036/

Q674B1075

Y594A1126.

A1309 44 Obsolete

. Arcoaire Air Conditioning and Heating logo;

T874A1036 part no. AO2076; includes Allen wrench and screws to lock cover.

A1317 44 Obsolete

. McQuay logo; part no. 60685301; no

T874A1036 scaleplate; used with Q674A-E,G.

A1325 75 Obsolete

. McQuay logo; part no. 60685401; no

T874A1036 Replacement does not have scaleplate; used with Q674C1306 and outdoor thermistor to display outdoor temperature.

A1341 44 Obsolete

. Trane logo; part no. THT-0577; meets DoD

T874A1176 specifications.

A1358 44 York-Miraco logo. T874A1036

A1366 51, 53 Obsolete

A1374 44 American Standard logo; part no. ASYSTAT610; heat

. BDP Multi-logo; part no. HH07AT182.

T874A1036

anticipator factory set at 0.4A.

A1390 44 Obsolete. Climate Control logo; part no. 654958804; °F/

T874A1036 Replacement has °F °C scaleplate.

A1416 44 Obsolete

. Reznor logo; part no. 654758803; °F/°C

T874A1036 Replacement has °F scaleplate.

A1424 214 Obsolete

no. HH07AT194; used with Q674B1455 (HH93AZ208).

A1440 91 Obsolete

. Carrier Olympia Series Split System logo; part

. Simplex System 2000 logo; heat anticipator

See OEM for replacement.

T874A1036 factory set at 1.2A; used with Q674G1005; used in Y594A.

A1465 212 Honeywell Trol-A-Temp™ logo; Premier White® color;

None See Trol-A-Temp for heat anticipator factory set at 0.10A; used with Q674E1379.

Both the thermostat and subbase must be replaced.

Set stage 1 heat anticipator for total current draw of fan and stage 1 heat primary; replacement has °F scaleplate.

scaleplate.

ability to display external temperature or momentary system switch position.

Replacement has two levers

and 1 speed fan.

ability to display external temperature or momentary system switch position.

Set stage 1 heat anticipator for total current draw of fan and stage 1 heat primary.

scaleplate.

replacement.

47 60-2485—8

Page 48

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 8. T874 Cross Reference.

Model

Number

A1481 44 Obsolete. Honeywell logo; Carrier part no. HH621602;

Fig.

No. Description

Trade Model

Replacement Remarks

T874A1036 includes locking cover and non-adjustable range stops set at 72°F (max. heat) and 78°F (min. cool).

A1507 44 Obsolete

. Climate-Tel logo; includes Allen wrench and

T874A1176 screws to lock cover and non-adjustable range stops set at 72°F (max. heat) and 78°F (min. cool).

A1523 224,

Obsolete

225

066804404; °F/°C scaleplate; no cooling anticipation;

. AAF/Snyder General logo; part no.

See OEM for replacement.

used with Q674E1312, C1298.

A1549 224,

A1556 51, 53 Carrier logo; part no. HH07AT164-W; °C scaleplate;

A1572 224,

A1580 91 California Economizer logo; Premier White® color; heat

Obsolete. McQuay logo; part no. 066816601; no cooling

225

anticipation; used with Q674E1312, C1298.

Premier White® color; includes Allen wrench and screws to lock cover; used with Q674B.

Obsolete

225

White® color; °F/°C scaleplate; no cooling anticipation.

. McQuay logo; part no. 066816611; Premier

See OEM for replacement.

T874A1036

See OEM for replacement.

T874A1036

Replacement has °F scaleplate; replacement is beige.

anticipator factory set at 1.2A.

A1598 224,

225

McQuay logo; part no. 073319001; Premier White® color; °F/°C scaleplate; includes Allen wrench, screws to

See OEM for replacement.

lock cover and AAF insert.

A1614 44 Honeywell logo; TRADELINE® model; °C scaleplate;

Premier White® color; includes Allen wrench and screws to lock cover; used with Q674B.

A1622 44 Obsolete

. York logo; part no. 2TH04703224A; includes

T874A1036 Replacement has °F

scaleplate; replacement is beige.

T874A1010 Allen wrench and screws to lock cover and nonadjustable range stops set at 72°F (max. heat) and 78°F (min. cool).

T874B 1-stage heat, 2-stage cool.

B1001 44 Obsolete. Honeywell logo. T874B1019

B1019 44 Honeywell logo; TRADELINE model; includes Allen

T874B1019 wrench and screws to lock cover.

B1027 44 Obsolete

B1035 44, 46 Obsolete

. Westinghouse logo. T874B1019

. Trane logo; used with Q674B1018, B1075;

T874B1019 used in Y594B1026, B1034.

B1043 44 Obsolete

. Honeywell logo; °C scaleplate. T874B1019 Replacement has °F

scaleplate.

B1050 44 Lennox logo; part no. 13F0201; °F/°C scaleplate. T874B1019 Replacement has °F

scaleplate.

B1068 44 Honeywell logo; Honeywell Canada TRADELINE model;

°C scaleplate; includes Allen wrench and screws to lock

T874B1019 Replacement has °F

scaleplate.

cover.

B1076 88 Obsolete

no. 91C7401; °F/°C scaleplate; used with Q674E1155.

B1084 44 Obsolete

°C scaleplate.

B1092 44 Obsolete

. Lennox Power Saver Two-Speed logo; part

. Lennox Two-Speed logo; part no. 13F0301;

. Honeywell logo; Heil Quaker part no.

T874B1019 Replacement has °F

scaleplate.

T874B1019 Replacement has °F

scaleplate.

T874B1019 HQ521389HW.

B1100 88 Obsolete

. Janitrol logo; part no. CHTS36-60; °F/°C

scaleplate; used with Q674E1338; used in Y594B1042.

B1118 44 Honeywell logo; °C scaleplate; used with

Q674A-E, G.

Both the thermostat and subbase must be replaced.

T874B1019 Replacement has °F

scaleplate.

T874B1019 Replacement has °F

scaleplate.

60-2485—8 48

Page 49

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 8. T874 Cross Reference.

Model

Number

B1134 222 Obsolete. Carrier Synergy 2000 logo; part no.

Fig.

No. Description

HH07AT199; °C scaleplate; used with Q674E1395 (HH93AZ209).

Trade Model

Replacement Remarks

T874B1019/

Q674E1049

Wiring differences (old=new):

W1=W; RC-RH jumper required; replacement has no LEDs.

T874C 2-stage heat, 1-stage cool.

C1000 44, 76 Honeywell logo; used with Q674B1075, C1181; used in

T874C1018

Y594C1058.

C1018 60, 61,

81, 92

Honeywell logo; TRADELINE model; includes Allen wrench and screws to lock cover; used with

T874C1018

Q674C1074.

C1026 44 Obsolete

wrench and screws to lock cover; non-adjustable range

. AAF logo; °C scaleplate; includes Allen

T874C1018 Replacement has °F

scaleplate.

stops set at 23°C (max. heat and min. cool) (73°F).

C1034 44 Lennox logo; part no. 13F0401; °F/°C scaleplate. T874C1018 Replacement has °F

scaleplate.

C1042 44 Obsolete

. Westinghouse logo; H1 anticipator factory set

T874C1018 at.75A; H2 anticipator factory set at 1.2A; used with Q674A-E,G.

C1059 44, 142 Obsolete

. Amana Air Conditioning logo; part no.

T874C1018 D68535-2; H1 anticipator factory set at 1.2A; used with Q674E1056, Q674B1059, Q674F1022; used in Y594C1009, Y594C1017, Y594C1256, Y594C1330.

C1067 44 Obsolete

scaleplate.

C1075 51, 53 Carrier logo; part no. HH07AT170; used with

Q674B1166.

. Sears logo; part no. 42. 9297; °F/°C

T874C1018 Replacement has °F

scaleplate.

Y594C1421 or

T874C1018

When using the T874C1018,

set stage 1 heat anticipator for total current draw of fan and stage 1 heat primary.

C1083 44 Obsolete

. Trane logo; used with Q674E1007; used in

T874C1018 Y594C1082.

C1117 44 Honeywell logo; °C scaleplate. T874C1018 Replacement has °F

scaleplate.

C1125 60, 61, 92Obsolete

. Honeywell logo; 12°F (6.7°C) differential

T8611M2025 between stage 1 heat and stage 2 heat; used with Q674G1047.

C1133 96 Obsolete

4ELN7546; no H1 heat anticipation; used with Q674A-

. AAF/Snyder General logo; part no.

T874C1018 Must have H1 anticipator set

to maximum value.

G,N and Q674C1173.

C1141 44 Obsolete

. Honeywell logo; meets DoD specs; includes

T874C1141 Allen wrench and screws to lock cover; no thermometer; non-adjustable range stops set at 72°F (max. heat) and 78°F (min. cool) (22-26°C); field adjustable locking levers.

C1158 44 Obsolete

C1166 51, 53 Obsolete

scaleplate; includes Allen wrench and screws to lock cover; used with Q674B.

. Solaron special. T874C1018

. Carrier logo; part no. HH07AT160; °C

T874C1018

Replacement has °F scaleplate; set stage 1 heat anticipator for total current draw of fan and stage 1 heat primary.

C1174 44 Obsolete

C1182 60 Obsolete

. Goettl logo. T874C1018

. Goettl logo; H1 anticipator factory set at 0.8A;

T874C1018 used with Q674N1015.

C1190 44 Obsolete

. Lennox logo; part no. 13F0501; °C scaleplate. T874C1018 Replacement has °F

scaleplate.

Both the thermostat and subbase must be replaced.

49 60-2485—8

Page 50

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 8. T874 Cross Reference.

Model

Number

Fig.

No. Description

Trade Model

Replacement Remarks

C1216 44 Obsolete. Fasco part no. 1230-8197. T874C1018

C1224 105 Obsolete. Square D logo. T874C1018

C1240 44 Honeywell logo; Honeywell Canada TRADELINE model;

°C scaleplate; includes Allen wrench and screws to lock

T874C1018 Replacement has °F

scaleplate.

cover.

C1257 44 Obsolete

differential between H1 and H2 heat.

. Singer part no. 0200-5931; 8°F (4.4°C)

T874C1125 Replacement has 12°F

differential between H1 and H2 heat.

C1265 44 Obsolete. Singer special; °C scaleplate; 5°C (8°F)

differential between H1 and H2 heat.

T874C1125 Replacement has 12°F

differential between H1 and H2 heat; replacement has °F scaleplate.

C1273 44 Honeywell logo; °C scaleplate; includes Allen wrench

and screws to lock cover; non-adjustable range stops

T874C1018 Replacement has °F

scaleplate.

factory set at 23°C (max. heat and min. cool) (73°F).

C1281 44 Obsolete

C1307 44 Obsolete

C1315 44 Obsolete

. Heat Wave special. T874C1018

. Friedrich Climate Master logo. T874C1018

. Wesco logo; heat anticipator factory set at

T874C1018

0.8A.

C1323 44 Obsolete

. Le Chauffage Urbain special; °C scaleplate. T874C1018 Replacement has °F

scaleplate.

C1331 82, 141 Obsolete

. Duotherm logo; used with Q674E or Q674F. T874C1018

C1349 61 Obsolete. Sigler logo; used with Q674N1023. T874C1018

C1372 52 Obsolete

. Honeywell logo; used with Q674B1190. T874C1018/

Q674B1034

For systems requiring automatic fan in cooling mode only.

T874C1018/

Q674B1075

For systems requiring automatic fan in heating and cooling.

C1398 105 Obsolete

Q674L1090.

. Fedders logo; °F/°C scaleplate; used with

Y594R1425

Wiring differences (old=new): K=E, C=X; replacement has °F scaleplate.

C1406 105 Obsolete

Q674L1090.

. Climatrol logo; °F/°C scaleplate; used with

Y594R1425

Wiring differences (old=new): K=E, C=X; replacement has °F scaleplate.

C1414 105 Obsolete

Q674L1090.

. Airtemp logo; °F/°C scaleplate; used with

Y594R1425

Wiring differences (old=new): K=E, C=X; replacement has °F scaleplate.

C1422 187 Obsolete

C1430 49 Obsolete

. Honeywell logo; used with Q674B1208. None

. Lennox Zone Master Two-Speed logo; part

T874C1018

no. 25F7201; used with Q674B1224.

C1448 110,

190

Obsolete

. Lennox logo; part no. 24F5101; meets DoD

specifications; requires outdoor reset; used with Q674L1165, L1355.

Y594R1763

Wiring differences (new=old): R=V-VR, Y=M, G=F, B-X, W=Y, T=A, O=R, X2=E; Emergency Heat becomes stage 1 heat source.

C1455 127 Obsolete

. Williamson logo; used with Q674L1322.

Y594R1243

C1463 82 Obsolete. AAF logo; °C scaleplate. T874C1018 Replacement has °F

scaleplate.

C1471 56 Obsolete

. Mammoth logo; part no. 71120102; used with

T874C1018

Q674B1257; used in Y594C1314.

Both the thermostat and subbase must be replaced.

60-2485—8 50

Page 51

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 8. T874 Cross Reference.

Model

Number

C1489 121 Obsolete. Honeywell logo; non-adjustable range stops

Fig.

No. Description

Trade Model

Replacement Remarks

Y594C1322 set at 75°F (max. heat and min. cool) (24°C); used with Q674L1157.

C1497 121 Obsolete. Honeywell logo; meets DoD specifications;

Y594C1322 used with Q674L1157.

C1513 44 Obsolete. Borg-Warner multi-logo; part no.

T874C1018

6TH11703124A.

C1562 44 Obsolete

. Honeywell logo; Heil Quaker part no.

T874C1018

HQ712001HW.

C1570 45 Obsolete

. Williamson logo; used with Q674B1000; used

T874C1018

in Y594C1280.

C1638 121 Obsolete

. Honeywell logo; meets DoD specifications;

Y594C1322 includes Allen wrench and screws to lock cover; no thermometer; non-adjustable range stops set at 72°F (max. heat) and 78°F (min. cool) (22-26°C); field adjustable locking levers; used with Q674L1561; used in Y594C1322.

C1653 70 Obsolete. Fiberglas Canada; °C scaleplate; no H1, H2,

or C1 anticipation; used with Q674S1000; used in

See OEM for

replacement. Y594C1348.

C1661 99 Obsolete. McQuay logo; part no. 61202401; °F/°C

scaleplate; includes momentary system switch position

T874C1125/

Q674B1075 with spring release; used with Q674C1363.

C1695 45 Obsolete

. Miller logo; used with Q674B1000; used in

T874C1018

Y594C1355.

C1703 45 Obsolete

. Intertherm logo; used with Q674B1000; used

T874C1018

in Y594C1363.

C1737 44 Obsolete

C1745 44 Obsolete

. Honeywell logo; Carrier part no. HH621603. T874C1018

. AAF/Snyder General logo; part no.

T874C1018

4ELN7919.

C1752 219 Obsolete

. McQuay/Snyder General logo; part no.

T8611M2025 061202402; 12°F offset between H1 and H2; °F/°C scaleplate; no C1 anticipation; used with Q674C1363.

C1760 44 Bard logo. T874C1018

C1778 219 Obsolete

066804405; 12°F offset between H1 and H2; °F/°C

. AAF/Snyder General logo; part no.

See OEM for

replacement. scaleplate; no C1 anticipation; used with Q674C1363.

C1794 53 Obsolete

. Carrier logo; Canada; part no. HH07AT160-W;

T874C1018 Set stage 1 heat anticipator for Premier White® color; °C scaleplate; includes locking cover.

C1802 246 Obsolete. California Economizer logo; °F/°C scaleplate;

T874C1018 used with Q674G1005; used in Y594C1371.

C1810 237 Obsolete

. Honeywell logo; TRADELINE model; Premier

Y594C1389 White® color; used with Q674B1547; used in Y594C1389.

C1844 238 Energy Night logo; used with Q674F1592; used in

Y594R1425 Jumper E-W2; system switch: Y594C1413.

C1851 60 Obsolete

C1869 219 McQuay logo; part no. 0073318801 Premier White®

color; °F/°C scaleplate.

Both the thermostat and subbase must be replaced.

. Whalen logo. T874C1018

See OEM for replacement.

Replacement has HEAT-OFF-

COOL system switching; no momentary system switch position; no LEDs.

total current draw of fan and stage 1 heat primary.

EM.HT.-HEAT-OFF-COOL.

51 60-2485—8

Page 52

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 8. T874 Cross Reference.

Model

Number

C1877 53 Obsolete. Honeywell logo; TRADELINE model; used

Fig.

No. Description

with Q674B1554; used in Y594C1421.

Trade Model

Replacement Remarks

Y594D1347 Jumper RC-RH; system

switch: OFF-HEAT-AUTOCOOL

T874D 2-stage heat, 2-stage cool.

D1009 166, 82 Obsolete

. Honeywell logo; used with Q674F1337,

T874D1165

E1007; used in Y594D1222, D1339.

D1017 44, 88 Obsolete

. Honeywell logo; TRADELINE model; includes

T874D1165 Allen wrench and screws to lock cover; used with Q674A-G and Q674E1155.

D1025 44 Obsolete

. Westinghouse logo; H1 anticipator factory set

T874D1165 at 0.75A; H2 anticipator factory set at 1.2A.

D1033 44 Lennox logo; part no. 13F0601; °F/°C scaleplate. T874D1165 Replacement has °F

scaleplate.

D1041 53 York logo; part no. 2TH04701524A; used with

T874D1165 Q674B1125.

D1058 44 Obsolete. Shiger special. T874D1165

D1066 44 Obsolete. ITT logo. T874D1165

D1074 51, 53,

Carrier logo; part no. HH07AT172; used with

146

Q674F1030 (HH93AZ174), F1063 (HH93AZ181) or Q674B.

D1082 44, 46,

48, 72

Trane logo; used with Q674B1018, C1009, B1075, B1133; used in Y594D1024, D1040.

D1090 44 Obsolete

D1108 44 Obsolete

D1116 76, 89, 94Obsolete

scaleplate; used with Q674C1116, E1197, G1104.

D1124 44 Obsolete

T874D1165

. Dunham-Bush logo. T874D1165

. Westinghouse logo. T874D1165

. Comfortmaker logo; part no. 1505-682; °F/°C

T874D1165 Replacement has °F

. Airtemp special. T874D1165

Set H1 anticipator for current draw of fan and stage 1 heat primary.

scaleplate.

D1132 44 Honeywell logo; °C scaleplate. T874D1165 Replacement has °F

scaleplate.

D1140 44 Obsolete

. Solaron special. T874D1165 Replacement has °F

scaleplate.

D1157 51, 53,

146

Carrier logo; part no. HH07AT172; °C scaleplate; used with Q674B or Q674F1030, F1063.

T874D1165

Replacement has °F scaleplate; set H1 anticipator for current draw of fan and stage 1 heat primary.

D1165 82 Honeywell logo; SUPER TRADELINE® model; includes

T874D1165 Allen wrench and screws to lock cover, field-adjustable range stops, field-adjustable locking levers.

D1173 51, 53 Trane logo; part no. BAY28X183; heat anticipator factory

set at 0.4A.

T874D1165

Set H1 anticipator for current draw of fan and stage 1 heat primary.

D1181 51, 53 Obsolete

Allen wrench and screws to lock cover and range stops set at 72°F (max. heat) and 78°F (min. cool).

D1199 44 Obsolete

. General Electric logo; locking cover includes

T874D1165

. Lennox logo; part no. 13F0701; °C scaleplate. T874D1165 Replacement has °F

Set H1 anticipator for current draw of fan and stage 1 heat primary.

scaleplate.

D1207 114 Obsolete

Q674L1199 and C815A1013 or Q674L1389.

. Lennox logo; part no. 24F5201; used with

T8611M2025

(programmable)

Wiring differences (old=new): V-VR=R, Y=W3, X=C, R=O, M=Y, M2=Y2-W2, F=G; jumper Y2-W2; no outdoor reset needed; use only one system transformer.

Both the thermostat and subbase must be replaced.

60-2485—8 52

Page 53

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 8. T874 Cross Reference.

Model

Number

D1215 44 Obsolete. Friedrich Climate Master logo; part no.

Fig.

No. Description

Trade Model

Replacement Remarks

T874D1165 Replacement has °F

AT5415; °F/°C scaleplate.

D1223 44 Honeywell logo; Honeywell Canada TRADELINE model;

T874D1165 Replacement has °F

Celsius scale.

D1231 44 Obsolete

. Honeywell logo; 12°F (7°C) differential

T874D1165 Replacement has 2°F

between H1 and H2.

D1249 44 Obsolete

. Fedders special. T874D1165

D1256 44 Obsolete. Climatrol special. T874D1165

D1264 107 Obsolete

no. HH07AT173; used with Q674L1116 (HH93AZ171).

D1272 51, 53 Obsolete

. Carrier Heat Pump System Control logo; part

. Carrier logo; part no. HH07AT162-03; °C

See OEM for replacement.

T874D1165

scaleplate; used with Q674B.

D1280 44 Obsolete

D1298 90, 232 Obsolete. Singer special; °C scaleplate; controls two

separate heat/cool circuits; used with Q674D or

. Command-Aire logo. T874D1165

See OEM for replacement.

Q674G1054, G1062.

D1306 90, 186 Obsolete

two separate heat/cool circuits; used with Q674G1013.

D1314 44 Obsolete

. Trane special; part no. 02005949; controls

. McQuay logo; part no. 02005941; 12°F

See OEM for replacement.

T874D1165 Replacement has °F

(6.6°C) differential between H1 and H2.

D1322 46 Obsolete

. Amana logo; part no. D68535-03; used with

T874D1165

Q674B1075; used in Y594D1149.

D1330 44 Obsolete

D1355 44 Obsolete

. Trane logo; part no. 13080242; °C scaleplate. T874D1165 Replacement has °F

. Climate Control special; part no. 02005942;

T874D1165 Replacement has 2°F °C scaleplate; 6°C (11°F) differential between H1 and H2.

D1363 44 Obsolete. McQuay logo; part no. 02005943; 12°F

T874D1165 Replacement has 2°F (6.6°C) differential between H1 and H2; 6°F (3.3°C) differential between C1 and C2.

D1405 44 Obsolete

. Trane logo; part no. 02005952; 12°F (6.6°C)

T874D1165 Replacement has 2°F differential between H1 and H2; 6°F (3.3°C) differential between C1 and C2.

D1413 44 Obsolete

. Trane logo; part no. 02005956; 12°F (6.6°C)

T874D1165 Replacement has 2°F differential between H1 and H2.

D1421 44 Obsolete

. Climate Control special; part no. 02005938;

T874D1165 Replacement has °F °C scaleplate.

D1439 90 McQuay logo; part no. 02005935; used with

T874D1165 Q674G1096.

D1447 90 Obsolete

. Climate Control special; part no. 02005940;

T874D1165 Replacement has °F °C scaleplate; used with Q674G1096.

D1454 51, 53 Obsolete

D1462 80 Obsolete

. Carrier logo.

. Fedders multi-logo; part no. THTX-220-A0HB,

T874D1165

T874D1165 88-58-00550-001; used with Q674E1205.

Both the thermostat and subbase must be replaced.

scaleplate.

differential between H1 and H2.

Replacement thermostat has °F scaleplate; set H1 anticipator for current draw of fan and stage 1 heat primary.

scaleplate; 2°F differential between H1 and H2.

scaleplate.

differential between H1 and H2.

differential between H1 and H2; 2°F differential between C1 and C2.

differential between H1 and H2.

scaleplate.

Set H1 anticipator for current draw of fan and stage 1 heat primary.

53 60-2485—8

Page 54

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 8. T874 Cross Reference.

Model

Number

D1470 44 Obsolete. York logo; part no. 2TH04701624A; includes

Fig.

No. Description

Trade Model

Replacement Remarks

T874D1165 Replacement has °F

Allen wrench and screws to lock cover; °C scaleplate.

D1488 44 Obsolete

D1496 44 Obsolete. Borg Warner multi-logo; part no.

. Risco special. T874D1165

T874D1165 6TH04701524A; includes Allen wrench and screws to lock cover.

D1504 82 York logo; part no. 025-23321-000; °C scaleplate; used

T874D1165 Replacement has °F with Q674E1007; used in Y594D1180.

D1512 44 Honeywell logo; Heil Quaker part no. HQ712002HW. T874D1165

D1520 44 Obsolete. Bard logo; adjustable lever stops set 68°F

T874D1165 (max. heat) and 78°F (min. cool).

D1538 44 Obsolete

D1553 44 Obsolete

. McQuay logo; part no. 02005937. T874D1165

. Climate Control special; part no. 02005944;

T874D1165 Replacement has 2°F °C scaleplate; 6°C differential between H1 and H2; 3°C differential between C1 and C2.

D1561 44 Obsolete

. General Electric logo; used with Q674 A-G. T874D1165

D1587 44 Obsolete. Stiles Four Seasons logo. T874D1165

D1595 139 Obsolete

. Nepco logo; used with Q674F1394. T874D1165/

Q674B1018

D1603 44 Obsolete. Arcoaire logo. T874D1165

D1611 44 Obsolete

. No logo; Friedrich part no. AT5411; °F/°C

T874D1165 Replacement has °F scaleplate.

D1629 82 Obsolete

. Reznor logo; °F/°C scaleplate; used with

T874D1165 Replacement has °F Q674E1007; used in Y594D1248.

D1678 44 Obsolete

. Honeywell logo; Saudi Oger special; °C

T874D1165 Replacement has °F scaleplate; one setpoint lever; used with Q674A-K.

D1686 98 Obsolete. McQuay logo; part no. 60685501; 8°F (4.4°C)

T874D1165 Replacement has 2°F differential between H1 and H2; 6°F (3.3°C) differential between C1 and C2; used with Q674E1312.

D1694 202 Obsolete

Q674G1120.

D1702 44 Obsolete

. McQuay logo; part no. 60685201; used with

See OEM for replacement.

. McQuay logo; part no. 60685101. T874D1165

D1710 44 Trane logo. T874D1165

D1728 44 York-Miraco logo. T874D1165

D1744 44 American Standard logo; heat anticipator factory set at

T874D1165

0.4A.

D1751 44 Obsolete

. Goettl logo; part no. 372080; range stops set

T874D1165 at 68°F (max. heating) and 78°F (min. cooling).

D1769 82 Obsolete

. Arcoaire logo; part no. 1506753; °F/°C

T874D1165 Replacement has °F scaleplate; used with Q674E1346; used in Y594D1297.

D1777 44 Obsolete

. Climate Control logo; part no. 65495806; °F/

T874D1165 Replacement has °F °C scaleplate.

D1785 82 Obsolete

. Comfortmaker logo; part no. 1505753; °F/°C

T874D1165 Replacement has °F scaleplate; used with Q674E1346; used in Y594D1305.

D1793 44 Obsolete

. McQuay logo; part no. 65495805; °F/°C

T874D1165 Replacement has °F scaleplate.

Both the thermostat and subbase must be replaced.

scaleplate.

differential between H1 and H2; 2°F differential between C1 and C2; replacement has °F scaleplate.

Replacement has HEAT-OFF-

COOL system switching; no LEDs.

scaleplate.

scaleplate; separate heating and cooling setpoint levers.

differential between H1 and H2; 2°F differential between C1 and C2.

scaleplate.

60-2485—8 54

Page 55

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 8. T874 Cross Reference.

Model

Number

D1801 45, 208 Trol-A-Temp by Honeywell logo; H1 and H2 anticipators

Fig.

No. Description

Trade Model

Replacement Remarks

None See Trol-A-Temp for

set at 0.10A; used with Q674B1463, D1115.

D1819 44 Marv Air Com Stat logo; part no. 50059; adjustable

T874D1165 Replacement has a 2°F fixed interstage between H1 and H2 and between C1 and C2; includes Allen wrench and screws to lock cover; field adjustable range stops; °F/°C scaleplate.

D1827 45, 208 Trol-A-Temp by Honeywell logo; Premier White® color;

None See Trol-A-Temp. H1 and H2 heat anticipators set at 0.10A; used with Q674B1471, D1123.

D1843 45 Obsolete

. Janitrol logo; Goodman part no. CHT 90-120;

T874D1165

used with Q674B1000; used in Y594D1321.

D1850 44 Honeywell logo; Carrier part no. HH621606. T874D1165

D1868 44 Bard logo; part no. 8405-031; H1 and H2 heat

T874D1165 Replacement has 2°F fixed anticipators factory set at 0.25A; 5°F interstage differential between H1 and H2 and between C1 and C2; includes Allen wrench and screws to lock cover; field adjustable range stops.

D1876 44 Obsolete

. AAF/Snyder General logo; part no.

T874D1165 Replacement has °F 4ELN6981A; °F/°C scaleplate.

D1892 44 Obsolete

D1918 224,

Obsolete

225

no cooling anticipation; used with Q674E1312, C1298;

. Climate-Tel logo. T874D1165

. AAF/Snyder General logo; °F/°C scaleplate;

See OEM for replacement.

66804407.

D1926 226 Obsolete. AAF/Snyder General logo; °F/°C scaleplate;

no cooling anticipation; used with Q674G1120;

See OEM for replacement.

66804406.

D1934 44 Bard logo. T874D1165

D1942 82 Honeywell logo; TRADELINE model; used with

Y594D1347 Q674E1403; used in Y594D1347; designed to replace York part no. 2TH04701024.

D1959 44 Rheem part no. 41-21444-01. T874D1165

D1967 44 Obsolete. Desert Aire logo. T874D1165

D1975 224,

D1983 226 Obsolete

Obsolete

225

scaleplate; no cooling anticipation.

. McQuay part no. 066816603; °F/°C

. McQuay part no. 066816602; °F/°C

scaleplate; no cooling anticipation; used with

See OEM for

replacement.

See OEM for

replacement. Q674G1120.

D1991 51, 53 Carrier logo; Premier White® color; °C scaleplate.

T874D1165

D2007 44 Ultra-Zone logo. T874D1165

D2023 44 Honeywell logo; TRADELINE model; Premier White®

T874D1165 Replacement has °F color; °C scaleplate; includes locking cover; used with Q674A-K.

D2031 82 Obsolete

Q674E1049 and TG504A1025; used in Y594D1354.

D2049 45, 72,

55, 66,

Both the thermostat and subbase must be replaced.

Obsolete no. HH07AT236; °F/°C scaleplate; used with Q674B-D,

184

Q674G; used in Y594D.

. Honeywell logo; no cover; used with

. Carrier Heat Pump System Control logo; part

T874D1165 or

Y594D1354

T874D1165 Replacement has °F

replacement.

interstage differential between H1 and H2 and between C1 and C2; replacement has °F scaleplate.

interstage differential between H1 and H2 and between C1 and C2.

scaleplate.

Set H1 anticipator for total current draw of fan and stage 1 primary; replacement has °F scaleplate.

scaleplate and is beige.

scaleplate.

55 60-2485—8

Page 56

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 8. T874 Cross Reference.

Model

Number

D2056 44 Obsolete. ComStat logo; part no. 50056; °F/°C

D2064 53 Obsolete

Fig.

No. Description

scaleplate; adjustable interstage on both heating and cooling; includes locking cover and field-adjustable locking levers.

. Carrier Weathermaker; part no. HH07AT209;

stage 1 and 2 heat anticipator factory set 0.1A; taupe color; used with Q674E1445; used in Y594D1412.

Trade Model

Replacement Remarks

T874D1165 Replacement has °F

scaleplate and 2°F fixed differential in heating and cooling.

T874D1165 Set stage 1 heat anticipator for

total current draw of fan and stage 1 heat primary. Replacement is beige.

D2072 53 Obsolete

taupe color; used with Q674E1445; used in Y594D1420.

. Carrier Zone Perfect; part no. HH07AT208;

T874D1165 Set stage 1 heat anticipator for

total current draw of fan and stage 1 heat primary. Replacement is beige.

D2080 139 Obsolete

D2098 44 Obsolete. Honeywell logo; °F scaleplate; one setpoint

lever; used with Q674D1008; used in Y594D1438.

. Hydroheat logo. T874D1165/

Q674B1018

T874D1165 Replacement has °F

Replacement system switch:

HEAT-OFF-COOL; no LEDs.

scaleplate and two setpoint levers

D2106 44 Obsolete

lever; used with Q674D1008; used in Y594D1446.

. Honeywell logo; °C scaleplate; one setpoint

T874D1165 Replacement has °F

scaleplate and two setpoint levers.

D2114 44 Obsolete

. Bard logo; °C scaleplate. T874D1165 Replacement has °F

scaleplate.

D2122 224,

225

Obsolete

. McQuay T874D2023 Replacement has °C

scaleplate.

T874D1165 Replacement has °F

scaleplate.

D2130 226 Obsolete

. McQuay See OEM for

replacement.

D2148 44 Obsolete

D2155 139 Hydroheat logo; Premier White® color; °F/°C scaleplate;

used with Q674F1634.

D2163 208 Obsolete

. Dry Aire Systems logo; °F/°C scaleplate. T874D1165

T874D1165/

Q674B1018

. Amana logo; part no. P1217501F; °F/°C

T874D1165

Replacement system switch:

HEAT-OFF-COOL; no LEDs.

scaleplate.

D2171 44 Obsolete

. Amana logo; part no. P1217701F; °F/°C

T874D1942

scaleplate.

D2189 44 Armstrong logo; part no. 01142A024; °F/°C scaleplate;

T874D1165

includes Air Ease insert.

D2197 44 Liebert logo; part no. 138968P3; °F/°C scaleplate;

T874D1165 interstage differential between H1 and H2 and between C1 and C2; includes Allen wrench and screws to lock cover; field-adjustable locking levers.

D2205 44 Aaon logo; Premier White® color; °F/°C scaleplate. T874D1165

T874E 0-stage heat, 2-stage cool.

E1008 44 Obsolete

E1016 44 Honeywell logo; TRADELINE model; includes Allen

. Honeywell logo. T874E1016

T874E1016 wrench and screws to lock cover; field-adjustable locking levers.

E1024 44 Obsolete

. Westinghouse logo. T874E1016

E1032 44 Lennox logo; part no. 13F0901; °F/°C scaleplate. T874E1016 Replacement has °F

scaleplate.

E1040 72 Obsolete

. Trane logo; used with Q674C1009; used in

T874E1016 Y594E1015.

Both the thermostat and subbase must be replaced.

60-2485—8 56

Page 57

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 8. T874 Cross Reference.

Model

Number

Fig.

No. Description

Trade Model

Replacement Remarks

E1081 44 Trane logo; part no. BAY28X186; °F/°C scaleplate. T874E1016 Replacement has °F

scaleplate.

E1099 44 Obsolete

. Lennox logo; part no. 13F1001; °C scaleplate. T874E1016 Replacement has °F

scaleplate.

E1107 44 Honeywell logo; °C scaleplate. T874E1016 Replacement has °F

scaleplate.

E1123 44 Obsolete. Amana logo; part no. D68535-4. T874E1016

E1149 44 Obsolete

E1156 44 Obsolete

. York logo; part no. 2TH04701724A. T874E1016

. Borg Warner multi-logo; part no.

T874E1016

6TH04701724A.

E1164 44 Obsolete

. E. A. Juffali & Bros. logo. T874E1016

E1206 44 Obsolete. Trane logo. T874E1016

E1230 44 Obsolete

. Climar logo. T874E1016

T874F 2-stage heat, 0-stage cool.

F1007 44 Honeywell logo. T874F1015

F1015 44 Honeywell logo; TRADELINE model; includes Allen

T874F1015 wrench and screws to lock cover; field-adjustable locking levers.

F1023 44 Obsolete

F1031 44 Obsolete

40003440-001 wallplate; used in Y594F1022.

F1049 44 Obsolete

. Lennox logo; part no. 13F1101. T874F1015

. Honeywell logo; °C scaleplate; used with

T874F1015 Replacement has °F

scaleplate.

. Lennox logo; °C scaleplate. T874F1015 Replacement has °F

scaleplate.

F1056 55,66Obsolete

. Honeywell logo; stages 1 and 2 heat

None

electrically isolated; used with Q674D1008.

F1072 44 Obsolete

. Wesco logo; heat anticipator factory set at

T874F1015

0.8A.

F1098 189 Obsolete

an M839.

F1106 95 Obsolete

. Lennox logo; used with Q674D1008 to control

. Oneida logo; part no. 30A0287-02; used with

T874F1015 Set H1 and H2 anticipators to

lowest settings.

T874F1155

Q674K1018 on combination wood and oil applications.

F1114 44 Honeywell logo; Honeywell Canada TRADELINE model;

°C scaleplate; includes Allen wrench and screws to lock

T874F1015 Replacement has °F

scaleplate.

cover; field-adjustable locking levers.

F1122 62 Obsolete

used with Q674B1307.

F1130 72, 91 Obsolete

Q674C, D, or G; used with Q674C1009, G1005; used in

. Honeywell logo; two heat setpoint levers;

. Reznor logo; °F/°C scaleplate; used with

T874F1015/

Replacement has no LED.

Q674D1040

T874F1015 Replacement has °F

scaleplate.

Y594F1048.

F1148 44 Obsolete

F1155 95 Honeywell logo; used with Q674K1026 on combination

. Trane logo; part no. THT 0584. T874F1015

T874F1155

wood and oil applications.

T874G Heat pump models; 2-stage heat, 1-stage cool;

1–stage changeover.

G1006 84, 155 Obsolete

. Honeywell logo; used with Q674E1015.

Y594G1252

Wiring differences (old=new): R=O, M=Y, F=G, V=R, Y=W2; E-W2 jumper required.

Both the thermostat and subbase must be replaced.

57 60-2485—8

Page 58

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 8. T874 Cross Reference.

Model

Number

Fig.

No. Description

G1014 86, 150 Obsolete. Lennox logo; part no. 24F5801; °F/°C

scaleplate; H2 anticipator factory set at 0.25A for fast cycle performance; changeover in cooling mode; independent heating and cooling circuits; used with Q674E1148, F1113.

G1022 86, 150 Obsolete

. Lennox logo; part no. 24F5701; °F/°C

scaleplate; H2 anticipator factory set at 0.25A for fast cycle performance; changeover in cooling mode; independent heating and cooling circuits; used with Q674E1148, F1113.

G1048 153,

Obsolete. Westinghouse logo; H2 anticipator factory set

159

at 1.2A; used with Q674F1121, J1019.

G1055 161 Carrier Heat Pump System Control logo; part no.

HH07AT171; H2 anticipator factory set at 0.8A; changeover in cooling mode; used with Q674J1035 (HH93AZ173).

G1071 50, 103,

Obsolete

126,

meets DoD specifications; H2 anticipator factory set at

183

0.8A; used with Q674P1005 (HH93AZ169), L1041

. Carrier Heat Pump System Control logo;

(HH93AZ175), B1158, or J1050.

G1089 154 Obsolete

. Marvair logo; special for Crispaire; H2

anticipator factory set at 1.2A; used with Q674F1204; used in Y594G1153.

G1097 155 Obsolete. Honeywell logo; Rheem part no. ZXMT-B79;

used with Q674F1238 (41-20797-14).

G1105 153 Obsolete. Heat Wave (Southwest Mfg.) logo; H2

anticipator factory set at 1.2A; used with Q674F1170.

G1113 1 03 Obsolete. Carrier Heat Pump System Control logo;

meets DoD specifications; H2 anticipator factory set at

0.8A; used with Q674L1041.

G1121 103 Obsolete

. Carrier Heat Pump System Control logo; part

no. HH07AT161; °C scaleplate; H2 anticipator factory set at 0.8A; includes Allen wrench and screws to lock cover.

G1139 143,

G1147 148 Obsolete

234

Obsolete C1108.

. Honeywell logo; used with Q674B1240,

. Honeywell logo; changeover in cooling mode;

used with Q674F1139.

G1154 84, 139 Obsolete

G1162 155 Obsolete

. Lennox logo; used with Q674E1015, F1105.

. Lennox logo; meets DoD specifications; used

with Q674F.

G1170 160 Obsolete

. York logo; part no. 2TH11702424A; H2

anticipator is fixed; used with Q674J1027; used in Y594G1013.

G1188 147 Obsolete. Honeywell logo; Keeprite/Westinghouse

special; H2 anticipator factory set 1.2A; °C scaleplate; changeover in cooling mode; used with Q674F1295.

G1196 160 Obsolete

. York logo; °C scaleplate; changeover in

cooling mode; used with Q674J1027; used in Y594G1138.

Both the thermostat and subbase must be replaced.

Trade Model

Replacement Remarks

Y594G1252

Wiring differences (old=new): R=O, M=Y, F=G, Y=W2, V-VR=R (must use single transformer).

Y594G1252

Wiring differences (old=new): R=O, M=Y, F=G, Y=W2, V-VR=R (must use single transformer).

Y594G1252

Wiring differences when replacing T874G/Q674J1019 (old=new): W=W2.

None See subbase description for

replacement information.

Y594G1419 Wiring differences (old=new):

C=X; jumper Y1-W1.

Y594G1393

Wiring differences (old=new): A=L.

Y594G1252

Y594G1419

Wiring differences (old=new): C=X; jumper Y1 -W1.

Y594G1419

Wiring differences (old=new): C=X; jumper Y1-W1.

None See subbase description for

replacement information.

Y594G1252

Wiring differences (old=new): C=X.

Y594G1252

See subbase description for replacement information.

Y594G1419

Y594G1567

Y594G1252

W1-Y1 jumper required.

Wiring differences (old=new): S=L.

Y594G1567

60-2485—8 58

Page 59

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 8. T874 Cross Reference.

Model

Number

G1204 162 Honeywell logo; designed for use on Trane heat pumps;

Fig.

No. Description

no H2 anticipation; changeover in cooling mode; used

Trade Model

Replacement Remarks

Y594G1161

Designed for use on Trane heat pumps.

with Q674J1043 and C815A1005; used in Y594G1161.

G1212 155 Obsolete

. Honeywell logo; H2 anticipator factory set at

Y594G1252

0.2A; changeover in cooling mode; includes shunt to bypass H2 anticipator with W3 heat relays; used with Q674F1238.

G1220 235 Obsolete. Rheem logo; part no. RXMT-C71; changeover

Y594G1252

in cooling mode; used with Q674F1238.

G1238 155 Obsolete. Ruud logo; part no. UXMT-C71; changeover

Y594G1252

in cooling mode; used with Q674F1238.

G1246 Obsolete. Honeywell logo; changeover in cooling mode.

155 Used with Q674F1212; used in Y594G1195, G1252,

Y594G1252

G1369.

170 Used with Q674F1410; used in Y594G1393.

Y594G1393

G1261 58, 157 Obsolete. Borg-Warner; used with Q674D1032, F1253. None See subbase description for

replacement information.

G1279 58, 157 Obsolete

. Bryant logo; used with Q674D1032, F1253. None See subbase description for

replacement information.

G1287 58, 157 Obsolete

. Wesco logo; used with Q674D1032, F1253. None See subbase description for

replacement information.

G1295 58 Obsolete

Q674D1032.

. York logo; part no. 2TH11702724A; used with

T874D1165/

Q674D1040

Wiring differences (old=new): Y=Y2, O=Y1, W=W2; jumper W1-Y2.

G1345 160 Obsolete

. York logo; part no. 2TH11702624A; °C

Y594G1575

scaleplate; used with Q674J1027.

G1352 73 Obsolete. Command-Aire logo; 12°F differential

between H1 and H2 for night setback; used with Q674C1066.

Y594H1012

Wiring differences (old=new): Y1=O, Y2=Y, L=R, R=none; RL jumper required; no night setback.

T8600D1004

(programmable)

Wiring differences (old=new): Y1=O, Y2=Y, L=RH; RC-RH jumper required; includes night setback.

G1378 79 Obsolete

0.8A; 12°F differential between H1 and H2 for night setback; °F/°C scaleplate; used with Q674C1124; used

. Mammoth logo; H2 anticipator factory set at

Y594H1012

Wiring differences (old=new): R1=none, R2=L; R-L jumper required; no night setback.

in Y594G1294.

T8090A1007/

Q682A1038a

Includes night setback; W-Y jumper required.

(programmable)

G1402 129 Obsolete

specifications; used with Q674L1363.

. York part no. 2TH11702824A; meets DoD

Y594R1425

Wiring differences (old=new): W=W2, X=E, B=X; jumper Y-W1 .

G1410 155 Obsolete

. Borg-Warner multi-logo; part

no. 6TH11703024A; used with Q674F1311.

G1428 160 Obsolete. Borg-Warner multi-logo; part no.

6TH11702424A; used with Q674J1027; used in

T874G1246

Y594G1252

Y594G1567

Y594G1229.

G1436 58 Obsolete. Borg-Warner multi-logo; part no.

6TH11702724A.

T874D1165/

Q674D1040

Wiring differences (old=new): Y=Y2, O=Y1, W=W2; jumper W1-Y2.

Both the thermostat and subbase must be replaced.

59 60-2485—8

Page 60

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 8. T874 Cross Reference.

Model

Number

Fig.

No. Description

G1444 160 Obsolete. ROCA logo; °C scaleplate; used with

Q674J1027.

G1451 155 Obsolete

. BDP multi-logo; part no. HH641502; used with

Q674F1212; used in Y594G1245.

G1469 194 Obsolete. No logo; Addison special; used with

Q674F1345; used in Y594G1344.

G1485 163 Obsolete

. AAF logo; part no. 4ELN-7839; °F/°C

scaleplate; 10°F differential between H1 and H2 for night setback and momentary RESET system switch position; used with Q674C1199.

G1493 167 Obsolete

. Honeywell logo; Rheem part no. 41-20797-18;

used with Q674F1360.

G1501 195 Obsolete. Coleman logo; part no. 3600-375; changeover

in cooling mode; used with Q674F1378.

G1535 163 Obsolete

. AAF/Snyder General logo; 4ELN7839 °F/°C

scaleplate; 10°F differential between H1 and H2 for night setback and momentary RESET system switch position; used with Q674C1199.

G1543 194 Obsolete

. Addison logo; Weather King part no. 8403-

197; used with Q674F1345; used in Y594G1328.

G1568 160 Obsolete

. Luxaire logo; part no. 026-00068-000; °C

scaleplate; used with Q674J1126; used in Y594G1351.

G1576 169 Obsolete

. Coleman logo; part no. 3600-373; changeover

in heating and cooling mode; used with Q674F1402; used in Y594G1377.

G1584 73 Obsolete. No logo; Friedrich part no. AT5784; 8°F

(4.4°C) differential between H1 and H2; used with Q674C1223.

G1592 155 Obsolete

. Arcoaire logo; used with Q674F1212; used in

Y594G1385.

G1600 199 Obsolete. Honeywell logo; meets DoD specifications;

used with Q674F1428; used in Y594G1401.

G1618 73 Obsolete

. Honeywell logo; 12°F differential between H1

and H2 for night setback; used with Q674C1256.

G1626 167 Honeywell logo; used with Q674F1436; used in

Y594G1526.

G1642 227 Honeywell logo; TRADELINE model; meets DoD

specifications; used with Q674F1444; used in Y594G1419.

Both the thermostat and subbase must be replaced.

Trade Model

Replacement Remarks

Y594G1567

T874G1246a or

V594G1252

Y594G1252

Replacement has °F scaleplate.

Wiring differences (old=new): Y1=O, C=X, W1=Y1, X=L.

Y594G1393

No night setback or momentary reset switch.

T8611G1004

(programmable)

Y594G1526

Y594G1252

Includes night setback; no momentary reset switch.

Wiring differences (old=new): L1=L; changeover in cooling only.

Y594G1393

No night setback or momentary reset switch.

T8611G1004

Includes night setback.

(programmable)

Y594G1252

Wiring differences (old=new): Y1=O, C=X, W1=Y, X=L.

Y594G1367

Replacement has °F scaleplate.

Y594G1633

Y594H1012

Wiring differences (old=new): Y1=O, Y2=Y, L=R, R=none; L-R jumper required; no night setback.

T8611G1004

Includes night setback.

(programmable)

T874G1246a or

Y594G1252

Y594G1419a

Wiring differences (old=new): jumper W1-Y1.

Y594H1012

Wiring differences (old=new): Y1=O, Y2=Y, L=R, R=none; L-R jumper required; no night setback.

T8600C1162

(programmable)

Wiring differences (old=new): L=R, W=O; W-Y jumper required; includes night setback.

None

Y594G1419

60-2485—8 60

Page 61

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 8. T874 Cross Reference.

Model

Number

Fig.

No. Description

G1659 177 Obsolete. Mammoth logo; 0.8A maximum current

through B or O terminal; 12°F differential between H1 and H2 for night setback; used with Q674C1330; used in Y594G1427.

G1675 174 Obsolete

. American Standard logo; part no. ASYSTAT650; used with Q674J1142; used in Y594G1443.

G1691 176 Obsolete. Command Aire logo; part no. P1013-0060;

12°F (6.6°C) differential between H1 and H2 for night setback; used with Q674C1389, C1397.

G1717 175 Obsolete

. Carrier Heat Pump System Control logo; part no. HH07AT102N; used with Q674J1167; used in Y507J1201.

G1741 227 Honeywell logo; TRADELINE model; includes factory

set range stops at 68°F (max. heat) and 78°F (min. cool); Premier White® color; used with Q674F1477; used in Y594G1476.

G1758 211 Trol-A-Temp by Honeywell logo; Premier White® color;

changeover is provided by Trol-A-Temp zone panel; used with Q674F1485; used in Y594G1492.

G1774 216 Obsolete. Comfortmaker logo; part no. 1505756; used

with Q674J1175; used in Y594G1500.

G1782 216 Obsolete

. Arcoaire logo; part no. 1506756; used with Q674J1175; used in Y594G1518.

G1790 161 Obsolete

. Carrier logo; Premier White® color; °C scaleplate; includes Allen wrench and screws to lock cover; used with Q674J1191.

G1816 163 Climate Master logo; part no. AT5716; °F/°C scaleplate;

10°F differential between H1 and H2 and momentary RESET system switch position.

G1824 227 Honeywell logo; Australian TRADELINE model; Premier

White® color; °C scaleplate; used with Q674F1477; used in Y594G1534.

G1832 231 Obsolete. Intertherm logo; used with Q674F1519; used

in Y594G1542.

G1840 231 Obsolete

. Miller logo; used with Q674F1519; used in Y594G1559.

G1857 229 Obsolete

. Lennox logo; °C scaleplate; Premier White® color; used with Q674F1535; used in Y594G1583.

G1865 160 Honeywell logo; TRADELINE model; designed to

replace Y594G1013 (York part no. 2TH11702424), Y594G1229 (York part no. 6TH11702424), and York part no. 2TH117704124); used with Q674J1209; used in Y594G1567.

Both the thermostat and subbase must be replaced.

Trade Model

Replacement Remarks

Y594H1012

Wiring differences (old=new): R2=L, R1=none; L-R jumper required; no night setback.

T8611G1004

Includes night setback.

(programmable)

Y594G1161

Y594H1012

Wiring differences (old=new): Y1=O, Y2=Y, R=none; L-R jumper required; no night setback.

T8611G1004

Includes night setback.

(programmable)

Y594G1252

Wiring differences (old=new): C=X, D=L; replacement has AUX. HEAT and EM. HEAT LEDs.

Y594G1476

None See Trol-A-Temp for

replacement.

Y594G1252

Wiring differences (old=new): E=W2, W1=W3, X=E, C=X.

Y594G1252

Wiring differences (old=new): E=W2, W1=W3, X=E, C=X.

Y594G1252

Wiring differences (old=new): C=X; replacement has °F scaleplate.

Y594G1393

Y594G1476

Y594G1252

No momentary reset switch.

Replacement has auto changeover in cooling mode only.

Y594G1252

Replacement has auto changeover in cooling mode only.

Y594G1161

Wiring differences (old=new): E=X2, C=B, L=F.

Y594G1567

61 60-2485—8

Page 62

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 8. T874 Cross Reference.

Model

Number

Fig.

No. Description

G1873 160 Obsolete. Honeywell logo; TRADELINE model; Premier

White® color; designed to replace Y594G1013 (York part no. 2TH11702424), Y594G1229 (York part no. 6TH11702424), and York part no. 2TH117704124); used with Q674J1225; used in Y594G1575.

G1881 167 Rheem; part no. 41-20797-18.

G1899 169 Obsolete. Amana; part no. 10574101; used with

Q674F1550; used in Y594G1591.

G1915 155 Econar logo; used with Q674F1212; used in

Y594G1609.

170 Used with Q674F1410.

G1923 176 Trane logo; part no. X13510599010; H2 make 12°F

below H1 make.

G1931 155,

G1949 73 Obsolete

Obsolete

170

scaleplate; used with Q674F1568.

. Honeywell logo; Premier White® color; °C

. Carrier Heat Pump System Control logo; part

no. HH07AT204; °F/°C scaleplate; H2 make 8°F below H1 make; used in Y594.

G1956 30, 103,

Obsolete

126,

°C scaleplate; includes locking cover.

. Carrier logo; Canada; Premier White® color;

183

G1964 160 York logo; Canada; Premier White® color; °C scaleplate;

used in Y594G1625.

G1972 169 Honeywell logo; TRADELINE model; used with

Q674F1584; used in Y594G1633.

G1980 169 Obsolete. Amana logo; part no. 10574103; used with

Q674F1600; used in Y594G1641.

G1998 155 Obsolete

. Tempstar logo (Inter-City Products); used in

Y594G1658; used with Q674F1212.

G2004 103 Honeywell logo; TRADELINE model; used with Q674L;

used in Y594G.

161 Used with Q674J1274; used in Y594G1674. Y594G1674

G2046 155,

WaterFurnace logo; part no. TA21H03; Premier White®

170

color; °F/°C scaleplate; used with Q674F1667; used in Y594G1716.

T874H Heat pump model; 1-stage heat, 1-stage cool,

1-stage changeover in cool.

H1005 74 Obsolete

. Command Aire logo; used with Q674C1041.

H1013 74 Obsolete. Friedrich part no. AT5813; °C scaleplate; used

with Q674C1041.

Both the thermostat and subbase must be replaced.

Trade Model

Replacement Remarks

Y594G1567

Y594G1526

Y594G1633

Y594G1252

Y594G1393

Y594H1012

Replacement is beige.

Wiring differences (old=new): Y1=O, Y2=Y, R=none; L-R jumper required; no night setback.

T8611G1004

Includes night setback.

(programmable)

None See subbase description for

replacement information.

Y594H1012

Wiring differences (old=new): Y1=O, Y2=Y, L=R, R=none; RL jumper required; no night setback.

T8600D1004

(programmable)

Wiring differences (old=new): Y1=O, Y2=Y, L=RH; RC-RH jumper required; includes night setback.

Y594G1476 Replacement has °F

scaleplate.

Y594G1575

Replacement has °F scaleplate.

Y594G1633

Wiring differences (old=new): W3=W2.

Y594G1252

Y594G1666

Y594G1716

Y594H1012

Wiring differences (old=new): Y1=O, Y2=Y; L-R jumper required.

Y594H1012

Wiring differences (old=new): Y1=O, Y2=Y; L-R jumper required; replacement has °F scaleplate.

60-2485—8 62

Page 63

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 8. T874 Cross Reference.

Model

Number

Fig.

No. Description

H1021 74 Obsolete. Friedrich Climate Master logo; part no.

AT5821; °F/°C scaleplate; used with Q674C1041.

H1039 79 Obsolete

. Mammoth logo; °F/°C scaleplate; used with Q674C1124; used in Y594H1004.

H1054 74 Obsolete

. No logo; Friedrich part no. AT5854; used with Q674C1041.

H1062 164 Honeywell logo; used with Q674C1249; used in

Y594H1012.

H1070 172,

Obsolete. Carrier Heat Pump System Control logo; part

173

no. HH07AT166; °C scaleplate; used with Q674B1406 (HH93AZ200) or Q674C1322 (HH93AZ199).

H1088 172,

173

Obsolete no. HH07AT167; used with Q674B1406 (HH93AZ200)

. Carrier Heat Pump System Control logo; part

or Q674C1322 (HH93AZ199).

H1096 177 Obsolete

. Mammoth Water Source Heat Pump logo; °F/ °C scaleplate; changeover stage 0.8A maximum; used B or O terminal; used with Q674C1330.

H1112 74 No logo; Friedrich part no. AT5812; used with

Q674C1355.

H1120 205 Obsolete

. Command Aire logo; part no. P1013-0055; used with Q674C1389, C1397.

H1138 221 Obsolete

. Climate Master logo; part no. AT5838; used with Q674C1470.

H1146 205 Trane logo; part no. X13510598010.

H1153 173 Obsolete

. Carrier Heat Pump System Control logo; part no. HH07AT167; °F/°C scaleplate; used with Q674C1322; used in Y594H1053.

H1161 74 Obsolete. Carrier Heat Pump System Control logo; part

no. HH07AT203; °F/°C scaleplate; used with Q674C1496; used in Y594H1038.

T874J Heat pump model. 2-stage heat, 1-stage cool.

J1002 124,

J1010 124,

J1028 124,

J1036 124,

J1044 124,

J1051 124,

Both the thermostat and subbase must be replaced.

Obsolete

144,

no. HH07AT175; used with Q674J1068 (HH93AZ183),

206,

Q674J1159 (HH93AZ196), Q674L1074 (HH93AZ186),

207

Q674L1637 (HH93AZ195).

Obsolete 2471; used with Q674J1084, L1371.

171

Obsolete

144,

no. HH07AT165; °C scaleplate; used with Q674J1068

206,

(HH93AZ183), Q674J1159 (HH93AZ196), Q674L1074

207

(HH93AZ186), Q674L1637 (HH93AZ195).

Obsolete

171

Q674J1217.

Obsolete Q674J1217.

171

Obsolete White® color; °C scaleplate.

144

. Carrier Heat Pump System Control logo; part

. BDP multi logo; part no. 34427DP124/P272-

. Carrier Heat Pump System Control logo; part

. Miller logo; part no. 9132230; used with

. Intertherm logo; part no. 9132240; used with

. Carrier logo; part no. HH07AT165-W; Premier

Trade Model

Replacement Remarks

Y594H1012

Wiring differences (old=new): Y1=O, Y2=Y; L-R jumper required; replacement has °F scaleplate.

Y594H1012

Wiring differences (old=new): R1=R, R2=L.

Y594H1012

Wiring differences (old=new): Y1=O, Y2=Y; L-R jumper required.

Y594H1012

None See subbase description for

replacement information.

None See subbase description for

replacement information.

Y594H1012

Wiring differences (old=new): R1=R, R2=L; L-R jumper required.

Y594H1012

Wiring differences (old=new): Y1=O, Y2=Y; L-R jumper required.

Y594H1012

Wiring differences (old=new): Y1=O, Y2=Y.

Y594H1012

Wiring differences (old=new): Y1=O, Y2=Y; replacement has MALFUNCTION LED only.

Y594H1012

Wiring differences (old=new): Y1=O, Y2=Y.

None See subbase description for

replacement information.

Y594H1012

Wiring differences (old=new): Y1=O, Y2=Y; L-R jumper required.

None See subbase description for

replacement information.

None See subbase description for

replacement information.

None See subbase description for

replacement information.

T8511G1021

None See subbase description for

replacement information.

63 60-2485—8

Page 64

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 8. T874 Cross Reference.

Model

Number

J1069 124,

Fig.

No. Description

Obsolete. Honeywell logo; TRADELINE model; used

144,

with Q674J1282; used in Y594J1019.

206,

207

J1077 124,

171

Obsolete scaleplate.

. Nordyne logo; part no. 9148300; °F/°C

T874K Heat pump model; 2-stage heat, 1-stage cool, automatic

changeover in heat.

K1001 77 Obsolete

K1019 181 Obsolete

. LSI Mammoth logo; used with Q674C1090.

. McQuay/Snyder General logo; part no.

60687301; °F/°C scaleplate; H1 anticipator set at 0.83A; 8°F interstage differential between H1 and H2 for night setback; used with Q674C1280.

K1027 181 Obsolete

. AAF/Snyder General logo; part no.

066804403; °F/°C scaleplate; H1 anticipator set at

0.83A; 8°F interstage differential between H1 and H2 for night setback; used with Q674C1280.

T874L Heat pump model; 2-stage heat, 1-stage cool,

changeover in cool.

L1000 198 Obsolete

. Carrier logo; part no. HH07AT176; used with

Q674E1270 (HH93AZ189).

L1018 138,

165

Obsolete HH07AT178; used with Q674B1356 (HH93AZ192) or

. Carrier Multiplex System logo; part no.

Q674C1264 (HH93AZ193).

L1026 198 Obsolete

. Honeywell logo; BDP part no. P272-2786;

used with Q674E1304.

L1034 203 Obsolete

. McQuay logo; part no. 60687201; °F/°C

scaleplate; H1 anticipator factory set at 0.83A; used with Q674C1280.

L1059 215,

213

Obsolete Q674B1448 (HH93A2202) or Q674C1413

. Carrier logo; part no. HH07AT192; used with

(HH93AZ204).

L1067 203 Obsolete

. AAF/Snyder General logo; part no.

066804402; H1 anticipator factory set at 0.83A; used with Q674C1280.

L1075 203 Obsolete

. McQuay logo; part no. 073318601; Premier

White® color; °F/°C scaleplate; includes AAF insert.

T874N Heat pump model; 2-stage heat; 1-stage cool plus

changeover; changeover in heat mode.

N1008 178 Obsolete

. Williamson logo; used with Q674F1196; used

in Y594N1007.

N1016 178 Honeywell Heat Pump Thermostat logo; used with

Q674F1220.

N1024 179,

Both the thermostat and subbase must be replaced.

Bard logo; H1 and C1 anticipation fixed; used with

217

Q674F1261.

Trade Model

Replacement Remarks

T8511G1021

Y594G1419

Wiring differences (old=new): RH-RC=R, W1=B, W3=W2, W2=W1; remove Y1-W1 jumper.

Y594G1252

Wiring differences (old=new): C=X, W=B, A=L; jumper E-W2; no night setback.

T8611G1004

(programmable)

Wiring differences (old=new): C=X, W=B, A=X2; jumper X2R; remove external time clock; includes night setback.

Y594G1252

Wiring differences (old=new): C=X, W=B, A=L; jumper E-W2; no night setback.

T8611G1004

(programmable)

Wiring differences (old=new): C=X, W=B, A=X2; jumper X2-R; remove external time clock; includes night setback.

Y594G1419

E-W2 jumper required.

See OEM for replacement.

Y594G1419

E-W2 jumper required.

Wiring differences (old=new): Y=Y1, W=B, A=X1; remove Y1-W1 jumper.

See OEM for replacement.

Y594G1419

Wiring differences (old=new): Y=Y1, W=B, A=X1; remove Y1-W1 jumper.

See OEM for replacement.

T874N1016

None See subbase description for

replacement information.

60-2485—8 64

Page 65

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 8. T874 Cross Reference.

Model

Number

N1040 179 Obsolete. Honeywell logo; H1 and C1 anticipation fixed;

Fig.

No. Description

Trade Model

Replacement Remarks

None

used with Q674F1261; used in Y594N1015.

N1057 178 Obsolete

. Intertherm logo; part no. 9111882; used with

T874N1016

Q674F1220; used in Y594N1023.

N1065 178 Obsolete

. Miller logo; Nordyne part no. 9122240; used

T874N1016

with Q674F1220; used in Y594N1031.

T874P Heat pump model; 2-stage heat, 1-stage cool, automatic

changeover in cool.

P1006 57, 78 Obsolete

. McQuay logo; part no. 860-442725B-00; 8°F

None See subbase description for (4.4°C) interstage differential between H1 and H2; used with Q674B1273, C1140.

P1014 78 Obsolete

scaleplate; 8°F (4.4°C) differential between H1 and H2

. Friedrich/Climate Master logo; °F/°C

T8600D2028

(programmable)

for night setback; used with Q674C1207.

P1022 97 Obsolete

. Friedrich/Climate Master logo; part no.

None See subbase description for AT5922; °F/°C scaleplate; 8°F (4.4°C) differential between H1 and H2 for night setback; used with Q674C1215.

P1030 97 Obsolete

. No logo; Friedrich part no. AT5930; 8°F

None See subbase description for (4.4°C) differential between H1 and H2 for night setback; used with Q674C1215.

P1055 68, 97 Obsolete. Carrier Heat Pump System Control logo; part

None See subbase description for no. HH07AT205; °F/°C scaleplate; heat interstage differential 8°F (4.4°C).

T874Q 1-stage heat; used with another T874 for night setback.

Q1005 44 Honeywell logo. T874A1036

Q1013 44 Obsolete

. Lennox logo; part no. 13F1201; °F/°C

T874A1036 Replacement has °F

scaleplate.

Q1021 44 Obsolete

. Lennox logo; part no. 13F1301; °C scaleplate. T874A1036 Replacement has °F

T874R Heat pump model; 2-stage heat, 1-stage cool, manual

changeover.

R1004 47 Obsolete

. Honeywell logo; used with Q674B1042; used

Y594R1243

in Y594R1029.

R1012 47 Obsolete

. Honeywell logo; Addison heat pump; used

Y594R1243

with Q674B1109.

R1020 102 Obsolete

. Lennox logo; part no. 24F5401; °F/°C

Y594R1243 scaleplate; H1 and C1 anticipators are fixed; auxiliary heat circuit powered by separate transformer; used with Q674L1025.

R1038 102 Obsolete

. Lennox logo; °C scaleplate; H1 and C1

Y594R1243 anticipators are fixed; auxiliary heat circuit powered by separate transformer; used with Q674L1025.

R1046 120,

Obsolete

101

anticipator is fixed; used with Q674L1272 in Y594R1011

. York logo; part no. 2TH11702224A; H2

Y594R1664

or with Q674L1094.

R1053 109 Obsolete. Honeywell logo; H2 anticipator is fixed; used

Y594R1763 with Q674L1140; used in Y594R1136.

R1061 104 Obsolete

. Honeywell logo; H2 anticipator is field

Y594R1243 adjustable; changeover in cooling; used with Q674L1082.

Both the thermostat and subbase must be replaced.

replacement information.

Wiring differences (old=new): L=R, W=O; W-Y jumper required; includes night setback.

replacement information.

scaleplate.

Wiring differences (old=new): W1=W2.

Wiring differences (old=new): M=Y, F=G, V-VR=R, Y=W2, R=O; replacement has °F scaleplate.

Designed for use on Trane heat pumps.

Replacement has auto fan in Emergency Heat mode.

65 60-2485—8

Page 66

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 8. T874 Cross Reference.

Model

Number

Fig.

No. Description

R1079 123 Obsolete. Ruud logo; part no. UXMT-C70; used with

Q674L1157.

R1087 120 Obsolete. Honeywell logo; Special for Dunham Bush;

use with Q674L.

R1095 123 Obsolete. Rheem logo; part no. RXMT-C70; used with

Q674L1157.

R1103 104 Obsolete. Westinghouse logo; used with Q674L.

R1111 116,

Obsolete. Marvair logo; H2 anticipator factory set at

104

1.2A; used with Q674L1215, L1082; used in Y594R1128.

R1129 113 Bard logo; used with Q674L1181.

R1137 108,

Obsolete

125

HQ711597HW; used with Q674L1132; used in

. Honeywell logo; Heil Quaker part no.

Y59 4R1110.

R1145 120 Obsolete. York logo; °C scaleplate; H2 anticipator is

fixed; used with Q674L1272; used in Y594R1102.

R1152 115 Honeywell logo; used with Q674L1207, L1033; used in

Y594R1243.

R1160 182 Obsolete. Honeywell Advanced Heat Pump System

logo; used with Q674L1298 and W89.

R1178 110,

111

Obsolete scaleplate; auxiliary heat circuit powered by separate

. Lennox logo; part no. 24F5601; °F/°C

transformer; fast cycle stage H2 anticipator; requires outdoor reset and independent circuits; used with Q674L1165, L1355.

R1186 182 Obsolete. Honeywell Advanced Heat Pump System

logo; used with Q674L1231 and W89.

R1194 115 Obsolete

. Amana logo; used with Q674L1249 and W89.

R1202 201 Obsolete. Intertherm logo; part no. 9111871; used with

Q674L1264 or Q674L1595; used in Y594R1185.

R1210 101 Obsolete

. Roca logo; °C scaleplate; used with

Q674L1017.

R1228 120 Obsolete

. York logo; part no. 2TH11702524A; °C

scaleplate; used with Q674L1272 and C815A1005; used in Y594R1144.

R1236 115 Obsolete. Williamson logo; includes Allen wrench and

screws to lock cover; used with Q674L1348.

R1244 115 Obsolete

. Westinghouse logo; used with Q674L1314

and W89.

R1251 120 Obsolete. York logo; part no. 2TH11702324A; H2

anticipator is fixed; used with Q674L1272 and C815A1039.

R1269 122 Obsolete. Fedders multi logo; part no.

THTX-120-HEHB 88-58-00540-001; used with Q674L1066; used in Y594R1037.

R1285 123 Obsolete

. Honeywell logo; Rheem part no. 41-20796-15;

used with Q674L1157.

R1301 113 Obsolete. Comfortmaker logo; part no. 1505-714; used

with Q674L1181; used in Y594R1417.

Both the thermostat and subbase must be replaced.

Trade Model

Replacement Remarks

Y594R1243

Y594R1664

T874R1152/

Y594R1243

Replacement has auto fan in Emergency Heat mode.

Y594R1243

Wiring differences (old=new): X1=X.

Y594R1292

Y594R1664

Y594R1243

None

Y594R1763

Wiring differences (old=new): V-VR=R, M=Y, F=G, X=B, Y=W, A=T, R=O, E=X2.

None

Y594R1243

Y594R1672

Wiring differences (old=new): W2=W, Z=no connection, K=X, W=G, W1=H, X=B.

Y594R1243

Wiring differences (old=new): W=W2, X=L, B=X.

Y594R1672

T874R1152

T874R1152/

Y594R1243

Y594R1672

Y594R1615

Wiring differences (old=new): K=E, C=X, W1=B, Z=L.

Y594R1243

Wiring differences (old=new): X1=X.

60-2485—8 66

Page 67

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 8. T874 Cross Reference.

Model

Number

R1319 191 Obsolete. Carrier part no. 42QH400083; used with

R1327 120 Obsolete

Fig.

No. Description

Q674B1281 on two speed fan applications.

. Borg-Warner multi-logo; part no.

Trade Model

Replacement Remarks

See OEM for

replacement.

Y594R1672 6TH11702224A; used with Q674L1272; used in Y594R1193.

R1335 106 Obsolete. BDP multi-logo; part no. HH641501; H2

Y594R1243 anticipator factory set 1.2A; used with Q674L1405; used in Y594R1201.

R1343 133 Obsolete. Fedders multi-logo; part no.

Y594R1425 THTX-120-HEHC 88-58-0056-001; used with Q674L1413; used in Y594R1219.

R1350 113 Obsolete. Honeywell logo; used with Q674L1181.

R1368 125 Obsolete

. Coleman logo; part no. 3600-368; used with

Y594R1243

Y594R1797 Q674L1421; used in Y594R1235.

R1376 115 Honeywell logo; °C scaleplate; used with Q674L1207. T874R1152

R1384 131,

Obsolete

135

no. HH07AQ170; used with Q674L (HH93AZ187),

. Carrier Heat Pump System Control logo; part

Y594G1243

Q674L (HH93AZ197), or Q674L (HH93AZ198).

R1392 128 Obsolete. Williamson logo; used with Q674L1447; used

Y594R1425 in Y594R1250.

R1400 113 Obsolete

. LSI part no. 104710001; used with

Q674L1181, L1462.

R1426 136 Obsolete

. Trane Weathertron Heat Pump logo; part no.

Y594R1763 BAYSTAT339 (WY28X0112); °F/°C scaleplate; used with Q674L1496; used in Y594R1284.

R1434 134 Ruud logo; part no. 41-20796-32; used with Q674L1504;

Y594R1300 used in Y594R1649.

R1442 134 Rheem logo; part no. 41-20796-28; used with

Y594R1300 Q674L1504; used in Y594R1631.

R1459 134 Obsolete. Honeywell logo; Rheem part no. 41-20796-25;

Y594R1300 used with Q674L1504.

R1467 108 Honeywell logo; used with Q674L1512; used in

Y594R1292 Y594R1292.

R1475 123 Honeywell logo; scale range 42°F to 88°F; used with

Y594R1300 Q674L1520; used in Y594R1300.

R1483 130 Obsolete. Comfortmaker logo; °F/°C scaleplate; used

Y594R1763 with Q674L1538 and C815A1005; used in Y594R1318.

R1491 137 Obsolete

. Honeywell logo; TRADELINE model; used

Y594R1615 with Q674L1553; used in Y594R1326.

R1509 47 Obsolete. Slant/Fin logo; used with Q674B1042; used in

Y594R1243 Y594R1334.

R1517 130 Obsolete

. Arcoaire logo; part no. 150671; used with

Y594R1763 Q674L1538 and C815A1005; used in Y594R1342.

R1525 113 Obsolete

. Arcoaire logo; used with Q674L1181; used in

Y594R1243 Y594R1359.

R1541 67 Obsolete

. Goettl logo; part no. 372071; used with

Y594R1300 Q674B1349.

R1558 134 Obsolete. Universal Parts logo; part no. 41-20796-45;

Y594R1300 used with Q674L1504; used in Y594R1623.

R1566 130 Obsolete. Honeywell logo; used with Q674L1538 and

Y594R1763 C815A1005; used in Y594R1375.

Both the thermostat and subbase must be replaced.

Wiring differences (old=new): K=E, C=X1, Z=L; remove Y1-W1 jumper.

Wiring differences (old=new): X1=X.

Wiring differences (old=new): C=X.

Wiring differences (old=new): A=L.

See subbase description for replacement information.

Wiring differences (old=new): W1=W, E=X2, X=F, C=B.

Wiring differences (old=new): W1=W2.

Wiring differences (old=new): W1=W, E=X2, X=F, C=B.

Wiring differences (old=new): X1=X.

Wiring differences (old=new): W1=W, E=X2, X=F, C=B.

67 60-2485—8

Page 68

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 8. T874 Cross Reference.

Model

Number

Fig.

No. Description

R1574 132 Obsolete. Comfortmaker logo; part no. 1505739; used

with Q674L1538; used in Y594R1383.

R1582 132 Obsolete

. Arcoaire logo; part no. 150739; used with

Q674L1538; used in Y594R1391.

R1590 115 Obsolete

. Refac logo; used with Q674L1207. T874R1152/

R1608 119 Obsolete. Honeywell logo; Intertherm heat pump; used

with Q674L1264; used in Y594R1409.

R1616 168 Honeywell logo; SUPER TRADELINE® model; used

with Q674L1587; used in Y594R1425.

R1624 200 Obsolete. Honeywell logo; used with Q674L1595; used

in Y594R1433.

R1632 134 Obsolete. Honeywell logo; used with Q674L1603.

R1640 115 Obsolete

. Hitecsa logo; °C scaleplate; H2 anticipator

factory set at 1.2A; used with Q674L1207.

R1657 136 Obsolete

. American Standard logo; part no.

ASYSTAT651; requires outdoor reset; used with Q674L1611; used in Y594R1441.

R1673 108 Heil logo; part no. 1060321, HAXB004TW01; used with

Q674L1132; used in Y594R1466.

R1699 119 Obsolete. Miller logo; used with Q674L1264; used in

Y594R1482.

R1707 209 Trol-A-Temp by Honeywell logo; Premier White® color;

used with Q674L1678; used in Y594R1490.

R1715 209 Trol-A-Temp by Honeywell logo; used with Q674L1186;

used in Y594R1508.

R1723 218 Obsolete

. No logo; Snyder General part no. 654958B07;

°F/°C scaleplate; used with Q674L1702 and C815A1005; used in Y594R1516.

R1731 108 Obsolete. Inter-City Products logo; part no.

HQ11477909HW; used with Q674L1132; used in Y594R1524.

R1749 108 Tempstar logo; part no. 1060322, TAXB004TW01; used

with Q674L1132; used in Y594R1532.

R1814 108 Obsolete. Honeywell logo; Keeprite part no. THPC; °C

scaleplate; used with Q674L1132; used in Y594R1607.

R1822 230 Honeywell logo; TRADELINE model; used with

Q674L1710; used in Y594R1615.

R1830 134 Obsolete. Addison logo; WeatherKing part no. 41-

20796-61; used with Q674L1504; used in Y594R1656.

R1855 228 Obsolete. Lennox logo; Premier White® color; °C

scaleplate; outdoor reset required (use C815A1005); used with Q674L1728; used in Y594R1714.

R1871 120 Honeywell logo; designed to replace Y594R1011 (York

part no. 2TH11702224); used with Q674L1736; used in Y594R1664.

Both the thermostat and subbase must be replaced.

Trade Model

Replacement Remarks

Y594R1243

Wiring differences (old=new): C=X, X=L, W=W2.

Y594R1243

Wiring differences (old=new): C=X, X=L, W=W2.

Replacement has °F

Y594R1243

Y594R1763

scaleplate.

Wiring differences (old=new): W2=W, X=B, Z=F, K=X2, W1=O.

Y594R1425

Y594R1243

Wiring differences (old=new): X=B, Z=F, W2=W, K=X2, W1=O.

Y594R1243a

Y594R1243

Replacement has °F scaleplate.

Y594R1763

Y594R1292

Y594R1763

Wiring differences (old=new): W2=W, X=B, Z=F, K=X2, W1=O.

None See Trol-A-Temp for

replacement.

None See Trol-A-Temp for

replacement.

Y594R1672

Wiring differences (old=new): W1=W, X=X2, C=B.

Y594R1292

Replacement has °F scaleplate.

Y594R1615

Y594R1300

Y594R1763

Wiring differences (old=new): Y1=Y, L=F, W1=W, E=X2, C=B; replacement has °F scaleplate.

Y594R1664

60-2485—8 68

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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 8. T874 Cross Reference.

Model

Number

R1889 120 Honeywell logo; designed to replace Y594R1151 (York

Fig.

No. Description

Trade Model

Replacement Remarks

Y594R1672 part no. 2TH11702324), Y594R1193 (York part no. 6TH11702224), and York part no. 2TH11704024; used with Q674L1736 and C815A1054; used in Y594R1672.

R1897 230 Honeywell logo; Premier White® color; used with

Y594R1680 Q674L1751; used in Y594R1680.

R1905 120 Obsolete. Honeywell logo; Premier White® color;

Y594R1672 designed to replace Y594R1151 (York part no. 2TH11702324), Y594R1193 (York part no. 6TH11702224), and York part no. 2TH11704024; used with Q674L1777 and C815A1054; used in Y594R1698.

R1913 120 Obsolete. Honeywell logo; Premier White® color;

Y594R1664 designed to replace Y594R1011 (York part no. 2TH11702224); used with Q674L1777; used in Y594R1706.

R1921 115 Obsolete

. Econar logo; used with Q674L1207; used in

Y594R1243 Y594R1722.

R1939 197 American Standard logo (Trane); part no.

Y594R1763 ASYSTAT651A; includes outdoor reset; used with Q7674L1801; used in Y594R1748.

R1947 168 Obsolete. Inter-City Products logo; part no.

Y594R1425 HQ1149406HW; used with Q674L1819; used in Y594R1755.

R1954 197 Honeywell logo; TRADELINE model; includes outdoor

Y594R1763 reset; used with Q674L1827; used in Y594R1763.

R1962 115 Obsolete

. Consolidated Industries logo; part no.

Y594R1680 9036100; Premier White® color; used with Q674L1843; used in Y594R1771.

R1970 120 York logo; Canada; Premier White® color; °C scaleplate;

Y594R1672 used in Y594R1789; used with C815A1039.

R1988 125 Honeywell logo; TRADELINE model; used with

Y594R1797 Direct replacement for

Q674L1868; used in Y594R1797.

R2002 245 Obsolete

. Amana Air Conditioning logo; part no.

Y594R1797 Wiring differences (old=new):

10574102; used in Y594R1805.

R2010 245 Obsolete

. Amana Air Conditioning logo; part no.

Y594R1797 Wiring differences (old=new):

10574104.

R2028 209 Obsolete

. York logo; part no. 2TH11703424A; used with

Y594R1797

Q674L1918 in Y594R1821.

R2036 134 Ruud logo; °C scaleplate; used with Q674L1504. See OEM for

replacement.

T874S 2-stage heat, 3-stage cool.

S1001 223 Obsolete

Control logo; used with Q674F1501.

. Carrier Synergy 2000 Heat Pump System

T8611M2025

(programmable)

or see OEM for

direct

replacement.

T874V 1-stage cool.

V1008 69 Obsolete

. No logo; Carrier part no. HH07AT177; used

T874A1036

with Q674R1003.

Both the thermostat and subbase must be replaced.

Replacement is beige.

Direct replacement for Y594R1748 (T874R1939/ Q674L1801) American Standard logo (ASYSTAT 651A) and Y594R1136 (T874R1053/Q674L1140).

Includes CHECK LED.

Replacement has °F scaleplate.

Y594R1235 (T874R1368/ Q674L1421) Evcon/Coleman part no. 3600-368.

C/X=X.

C/X=X, W3=W2.

Includes night setback.

69 60-2485—8

Page 70

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 8. T874 Cross Reference.

Model

Number

Fig.

No. Description

T874W 3-stage heat, 2-stage cool, manual changeover.

W1007 118 Obsolete. Honeywell logo; Westinghouse special; used

with Q674L1256.

W1015 54 Honeywell logo; used with Q674B1216 and C815A1005;

used in Y594W1014.

W1023 233 Obsolete

. Lennox Advanced Heat Pump System logo;

used with Q674L1280 and W89.

W1031 140 Obsolete

. No logo; Rheem part no. 41-20797-20; used

with Q674L1546 and C815A1005; used in Y594W1022.

W1049 100 Obsolete

. McQuay logo; part no. 61202501; 12°F

interstage differential between H2 and H3 for night setback; used with Q674C1363.

W1056 220 Obsolete. McQuay/Snyder General logo; part no.

1202501; 12°F differential between H2 and H3 for night setback; used with Q674C1363 (61202502).

W1064 220 Obsolete

. AAF/Snyder General logo; part no.

066804408; 12°F differential between H2 and H3 for night setback; used with Q674C1363 (66804408).

W1072 140 Obsolete

. Honeywell logo (Inter-City Products); used in

Y594W1030.

W1080 220 McQuay logo; part no. 073318901; Premier White®

color; 12°F differential between H2 and H3 for night setback.

W1106 247 Obsolete

. Addison logo; part no. 843-277; °F/°C

scaleplate; used with Q674L1934 in Y594W1055.

T874Y Heat pump model; 2-stage heat, 2-stage cool, heat or

cool auto changeover.

Y1005 210 Obsolete

. Mammoth Water Source Heat Pump logo;

used with Q674E1353; used in Y594Y1004.

Y1013 248 Obsolete

. WaterFurnace logo; part no. TA21H03;

Premier White® color; °F/°C scaleplate; used with Q674F1675 (32003081).

Both the thermostat and subbase must be replaced.

Trade Model

Replacement Remarks

T8611M2025

Includes night setback.

(programmable)

T874W1015

T8611M2025

Includes night setback.

(programmable)

T8611M2025

Includes night setback.

(programmable)

See OEM for replacement.

T8611M2025

Includes night setback.

(programmable)

None

T8611M2025

See OEM for replacement.

60-2485—8 70

Page 71

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 9. Q674 Subbase Cross Reference.

Model

Number

Fig.

No. Description

Q674 Trade

Replacement Remarks

Q674A System: HEAT-AUTO-COOL; Fan: AUTO-ON

A1001 71 Standard OEM. Q674A1019

A1019 71 TRADELINE® model; used with T874A-D. Q674A1019

A1035 71 Obsolete

. Trane part no. BAS-0435; used with T874A-D. Q674A1019

A1043 71 Honeywell logo; TRADELINE model; Q674A1019

A1050 71 Obsolete

. Standard OEM. Q674A1043

Q674B System: HEAT-OFF-COOL; Fan: AUTO-ON

B1000 45 Standard OEM; used with T874C1570, C1695, C1703,

Q674B1034

D1843; used in Y594C1363.

B1018 44 Standard OEM; used with T874B1035, D1082; used in

Q674B1018

Y594B1026, D1016.

B1026 45 Obsolete

. System: HEAT-OFF-RESET-COOL. Q674B1034

B1034 45 TRADELINE Q674B1034

B1042 47 Obsolete

. Used with T874R1004, R1509; used in

Y594R1243

Y594R1029, R1334.

B1059 45 Obsolete

. Factory installed RC-RH jumper; used with

Q674B1034 Field wire RC-RH.

T874C1059; used in Y594C1256.

B1075 46 Auto fan in heating and cooling mode; used with

Q674B1075

T874B1035, C1000, D1082; used in Y594D1040.

B1083 51 Obsolete

. Carrier part no. HH93AZ178; factory

Q674B1075

installed RC-RH jumper.

B1091 45 Obsolete

. Carrier part no. HH93AZ184; factory

Q674B1034

installed RC-RH jumper.

B1109 47 Obsolete

B1117 44 Obsolete

. Addison heat pump; used with T874R1012.

. Carrier part no. HH93AZ180; factory

Y594R1243

Q674B1018

installed RC-RH jumper.

B1125 53 Obsolete. York part no. 2TB04700324A; used with

Q674B1075

T874D1041.

B1133 48 Obsolete

. Includes FILTER LED; used with

Q674B1018

T874D1082; used in Y594D1156.

B1141 51 Trane part no. BAY28X185; automatic fan operation in

Q674B1075 Set T874 H1 anticipator for

heat and cool mode.

B1158 50 Obsolete

. Used with T874G1071. T874C1018/

Q674B1018

B1166 249 Carrier part no. HH93AZ179; factory installed RC-RH

jumper; LOCKOUT LED; used with T874C1075

Y594C1421 or

Q674B1075

(HH07AT170).

B1190 52 Obsolete. Wards special; factory installed RH-RC and

F-W3 jumpers; used with T874C1372.

Gas Furnace:

Q674B1034

Electric Furnace:

Q674B1075

B1208 187 Obsolete

B1216 54 Used with T874W1015 and C815A1005; used in

. Used with T874C1422. None

Q674B1216

Y594W1014.

B1224 49 Obsolete

. Lennox part no. 25F7301; four LEDs; used

Q674B1034 Replacement has no LEDs.

with T874C1430.

Both the thermostat and subbase must be replaced.

Wiring differences (old=new): W1=W2.

One system transformer only.

Wiring differences (old=new): W1=W2.

Jumper RC-RH; replacement has no LOCKOUT LED.

combined load of heat relay and fan relay.

W1-Y1 and RH-RC jumpers

required.

Replacement only requires

one transformer and has no LOCKOUT LED.

71 60-2485—8

Page 72

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 9. Q674 Subbase Cross Reference.

Model

Number

B1240 234 Obsolete. Northrup heat pump; AUX HEAT LED; used

Fig. No. Description

with T874G1139.

Q674 Trade

Replacement Remarks

Y594G1252

Wiring differences (old=new): Y1=Y2, W1=W2; EM HT system switch position is not operational.

B1257 56 Obsolete

. LSI-Mammoth; RESET LED; automatic fan

Q674B1075 Replacement has no LED. operation in heat and cool modes; used with T874C1471; used in Y594C1314.

B1273 57 Obsolete. McQuay part no. 860-442727B-00; System:

OVERRIDE-HEAT-OFF-COOL; used with T874P1006.

T874A1036/

Q674B1075

Wiring differences (old=new):

Y=Y1, L=R, W=O; jumper Y1W1; no night setback.

T8600D2028

(programmable)

Wiring differences (old=new): L=R, W=O; W-Y jumper required; night setback.

B1281 191 Obsolete

OFF-COOL; Fan: LOW-HI-CONT; international

. Carrier no. 42QH400103; System: HEAT-

See OEM for replacement.

symbols on switches; used with T874R1319.

B1299 46 Obsolete. Heil Quaker part no. HQ521714HW. Q674B1075

B1307 62 Obsolete

B1315 68 Obsolete

SERVICE LEDs; used with T874P1022, P1030.

. Includes two LEDs; used with T874F1122. T874F1015/

Q674D1040

. Friedrich part no. AQ5215; OVERRIDE and

T8600D2028

(programmable)

Replacement has no LEDs.

Wiring differences (old=new): L=R, W=O; W-Y jumper required; set dual fuel switch to electric heat; night setback.

B1331 65 Obsolete

B1349 67 Obsolete. Goettl part no. 372072; used with

. Includes two LEDs; used with T874A1002. Q674B1034 Replacement has no LEDs.

Y594R1300

T874R1541.

B1356 138 Obsolete. Carrier part no. HH93AZ192; used with

T874L1018 (HH07AT178).

B1372 44 Obsolete

B1380 46 Obsolete

B1398 48 Obsolete

. Trane part no. BAS-0427; used with T874A-D. Q674B1018

. Trane part no. BAS-0426; used with T874A-D. Q674B1075

. Trane part no. BAS-0431; FILTER LED; used

See OEM for replacement.

Q674B1034 Replacement has no LEDs. with T874A-D.

B1406 172 Obsolete

CHECK FILTER LEDs; used with T874H1070 (HH07AT166), T874H1088 (HH07AT167) or

. Carrier part no. HH93AZ200; FAULT and

T874A1150/

Q674B1075

Wiring differences (old=new):

Y=Y1; jumper W1-Y1; replacement has no LEDs.

T874H1153 (HH07AT167); used in Y594H1046.

B1414 51 American Standard (Trane) part no. ASYSTAT1617. Q674B1075

B1448 215 Obsolete

High-On; used with T874L1059.

B1455 214 Obsolete

High-On; used with T874A1424 (HH07AT194).

. Carrier part no. HH93A2202; Fan: Lo-Med-

. Carrier part no. HH93AZ208; Fan: Lo-Med-

See OEM for replacement.

B1463 45 Trol-A-Temp; used with T874D1801. None See Trol-A-Temp.

B1471 45 Trol-A-Temp; used with T874D1827. None See Trol-A-Temp.

B1513 53 Obsolete

Q674B1125 (York part no. 2TB04700324).

B1521 53 Obsolete

gray color; includes LOCKOUT LED and removable jumpers between RC and RH terminals.

B1539 45 Obsolete

. TRADELINE; exact replacement for

. Carrier Canada part no. HH93AZ179-W;

. Carrier part no. HH93AZ139; used with

Q674B1075 Jumper RC-RH; replacement

has no LOCKOUT LED.

Q674B1075 Jumper RC-RH; replacement

has no LOCKOUT LED; beige color.

Q674B1034 T874D2049; used in Y594D1370.

B1547 237 Obsolete

. TRADELINE; gray color; used with

Y594C1389 T874C1810; used in Y594C1389.

Both the thermostat and subbase must be replaced.

60-2485—8 72

Page 73

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 9. Q674 Subbase Cross Reference.

Model

Number

B1554 82 Obsolete. TRADELINE; includes LOCKOUT LED and

B1562 45 Obsolete

Fig.

No. Description

removable jumpers between RC and RH terminals; used with T874C1877; used in Y594C1421.

. Amana logo; part no. P1217701F;

Q674 Trade

Replacement Remarks

Y594D1347 Jumper RH-RC; system

switch: Off-HEAT-AUTOCOOL.

Q674B1034

removable jumpers between RC and RH terminals.

B1570 45 Obsolete

. Armstrong logo; part no. 03299A18. Q674B1034 Replacement is beige.

B1588 45 Obsolete. Standard OEM. Q674B1034 Replacement is beige.

Q674C System: OFF-AUTO; Fan: AUTO-ON

C1009 72 Standard OEM; used with T874D1082; used in

Q674C1058

Y594D1024.

C1017 Obsolete

. Includes factory-installed RC-RH jumper;

Q674C1058

used with T874A,F,Q.

C1033 72 Trane part no. BAY28X187. Q674C1058

C1041 74 Obsolete

T874H1005, H1054.

. Command Aire heat pump; used with

Y594H1012

Wiring differences (old=new): Y1=O, Y2=Y; W-Y jumper required.

C1058 72 TRADELINE Q674C1058

C1066 73 Obsolete

T874G1352.

. Command Aire heat pump; used with

Y594H1012

Wiring differences (old=new): Y1=O, Y2=Y, L=R, R=none; RL jumper required; no night setback.

T8600D2028

(programmable)

Wiring differences (old=new): Y1=O, Y2=Y, L=R; W-Y jumper required; night setback.

C1074 81 Obsolete

C1090 77 Obsolete. LSI-Mammoth heat pump; used with

T874K1001.

. Used with T874C1018. Q674C1058 Jumper W2-Y1 and RH-RC.

Y594R1419

Wiring differences (old=new): RH-RC=R, W1=B, W3=W2, W2=W1; remove Y1-W1 jumper.

C1108 143 Obsolete

T874G1139.

C1116 76 Obsolete

. Northrup special; AUX HEAT LED; used with

. McQuay part no. 02005959; two LEDs; used

Y594R1243

Q674C1058 Replacement has no LEDs.

Wiring differences (old=new): Y1=Y, W1=W2, C=X.

with T874D1116.

C1124 79 Obsolete

used with T874G-H; used in Y594G-H.

C1132 75 Obsolete

momentary system switch position; used with

. LSI-Mammoth heat pump; RESET LED;

. McQuay part no. 03005049; spring return

Y594G1294

T8600D2028

See OEM for replacement.

T874A1283.

C1140 78 Obsolete. McQuay no. 860-442728B-00; System:

OVERRIDE-AUTO-OFF; used with T874P1006.

T8600D2028

(programmable)

Wiring differences (old=new): L=R, W=O; W-Y jumper required; night setback.

C1157 72 Obsolete

C1165 192 Obsolete

momentary system switch position.

C1173 96 Obsolete

. York part no. 2TB04700124A. Q674C1058

. McQuay part no. 03005050; spring return

See OEM for replacement.

. American Air Filter part no. 4ELN-8787; used

Q674C1058 Replacement has no LEDs.

with T874C1133.

C1181 76 Obsolete

C1199 163 Obsolete

. California heat pump; used with T874C1000. Q674C1058

. American Air Filter part no. 4ELN-8788; two

T8600D2028

No momentary reset switch. LEDs; spring return momentary system switch position; used with T874G1485, G1535.

Both the thermostat and subbase must be replaced.

73 60-2485—8

Page 74

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 9. Q674 Subbase Cross Reference.

Model

Number

C1207 78 Obsolete. Friedrich; System: OVERRIDE-AUTO-OFF;

C1215 97 Obsolete

Fig. No. Description

used with T874P1014.

. Friedrich part no. AQ5315; System:

OVERRIDE-AUTO-OFF; OVERRIDE and SERVICE

Q674 Trade

Replacement Remarks

T8600D2028

(programmable)

T8600D2028

(programmable)

LEDs; used with T874P1022, P1030.

C1223 73 Obsolete

. Friedrich part no. AQ5323; used on systems

Y594H1012 requiring night setback contacts; used with T874G1584.

T8600D2028

(programmable)

C1249 164 Includes MALFUNCTION LED; used with T874H1062;

Y594H1012 used in Y594H1012.

C1256 73 Obsolete. Used with T874G1618.

Y594H1012

T8600D2028

(programmable)

C1264 165 Obsolete

T874L1018 (HH07AT178).

C1280 181,

C1298 76,

Obsolete

203

COMP FAULT LED; used with T874K1019, L1034.

Obsolete

225

used with T874A1523, A1549, D1918.

C1306 75 Obsolete

spring return momentary system switch position; used

. Carrier part no. HH93AZ193; used with

. McQuay heat pump; part no. 60687401;

. McQuay part no. 60684801; SERVICE LED;

. McQuay part no. 60685001; SERVICE LED;

See OEM for replacement.

T8600D2028 See thermostat description for

See OEM for replacement.

with T874A1325.

C1314 72 Obsolete. Trane part no. BAS-0429; used with T874A-F. Q674C1058

C1322 173 Obsolete

. Carrier part no. HH93AZ199; FAULT and CK

Y594H1012 FILTER LEDs; used with T874H1070 (HH07AT166), T874H1088 (HH07AT167) or T874H1153 (HH07AT167); used in Y594H1053.

C1330 177 Obsolete

. LSI-Mammoth part no. 71115201; RESET

Y594H1012 LED; used on systems with night setback contacts; used with T874G1659, H1096; used in Y594G1427, H1020.

C1355 74 Friedrich part no. AQ355; SERVICE LED; used with

Y594H1012 T874H1112.

C1363 99 Obsolete

auto fan in heat and cool mode; used with T874C.

219 Obsolete

. McQuay part no. 61202601; SERVICE LED;

T874C1125/

Q674B1075

. Used with T874C. See OEM for

replacement.

220 Obsolete

. Used with T874W. See OEM for

replacement.

100 Obsolete

. Used with T874W. T8611M2025

(programmable)

C1371 72 American Standard part no. ASYSTAT616. Q674C1058

Both the thermostat and subbase must be replaced.

Wiring differences (old=new): L=R, W=O; W-Y jumper required; night setback.

Wiring differences (old=new): Y1=O, Y2=Y, L=R, R=none; RL jumper required; no night setback.

Wiring differences (old=new): L=R, W=O; W-Y jumper required; night setback.

Wiring differences (old=new): Y1=O, Y2=Y, L=R, R=none; RL jumper required; no night setback.

Wiring differences (old=new): L=R, W=O; W-Y jumper required; night setback.

replacement information.

Wiring differences (old=new): 2=X.

Wiring differences (old=new): R1=R; R2=L.

Wiring differences (old=new): Y1=O, Y2=Y; L-R jumper required.

Replacement has HEAT-OFF-

COOL.

Includes night setback.

60-2485—8 74

Page 75

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 9. Q674 Subbase Cross Reference.

Model

Number

C1389 205,

C1397 205,

C1413 213 Obsolete

C1439 217 Obsolete

C1454 163 Obsolete

Fig.

No. Description

Obsolete. Command Aire part no. P1099-0021; two

176

LEDs; used with T874G-H.

171

Obsolete with T874G-H.

. Command Aire part no. P1099-0023; used

. Carrier part no. HH93AZ204; Fan: Lo-Med-

High-On; used with T874L1059.

. Bard part no. 8404-016; used with

T874N1024.

. Climate Master part no. AQ5354; two LEDs;

Q674 Trade

Replacement Remarks

None See thermostat description for

replacement information.

None See thermostat description for

replacement information.

See OEM for replacement.

Y594G1393

No momentary reset switch.

spring return momentary system switch position.

C1462 25 Climate Master Special. Q674C1058 Replacement has no LEDs.

C1470 221 Obsolete. Climate Master part no. RQ5370; used with

T874H1138.

Y594H1012

Wiring differences (old=new): Y1=O, Y2=Y; replacement has MALFUNCTION LED only.

C1496 74 Obsolete. Carrier part no. HH93AZ213; includes

SERVICE LED; used with T874H1161; used in Y594H1038.

C1504 83 Obsolete

. Carrier part no. HH93AZ214; used in Y594.

Y594H1012

Wiring differences (old=new): Y1=O, Y2=Y; L-R jumper required.

Wiring differences (old=new): Y1=O, Y2=Y, L=R, R=none; RL jumper required; no night setback.

T8600D2028

(programmable)

Wiring differences (old=new): Y1=O, Y2=Y, L=R; W-Y jumper required; night setback.

C1512 97 Obsolete

Override-Auto-Off; includes two LEDs; used in Y594.

. Carrier part no. HH93AZ216; System:

T8600D2028

(programmable)

Wiring differences (old=new): L=R, W=O; W-Y jumper required; night setback.

C1520 72 Obsolete. Carrier part no. HH93AZ210; used with

Q674C1058

T874D2049; used in Y594D1388.

C1538 163 Climate Master part no. AQ5354; System: Off-Auto-

Y594G1393 No momentary reset switch. Override; includes two LEDs and momentary spring position.

C1546 76,

225

C1553 181,

203

Obsolete

. McQuay part no. 060684802; gray color;

includes one LED.

Obsolete

. McQuay logo; part no. 073319901; includes

one LED.

Q674C1058 Replacement has no LEDs;

beige color

Q674C1058 Replacement is beige.

C1561 76 McQuay logo; part no. 073319701; includes one LED. See OEM for

replacement.

C1579 99,

C1595 72 Obsolete

McQuay logo; part no. 073320001; includes one LED. See OEM for

100

. Standard OEM. Q674C1058

replacement.

Q674D System: None; Fan: None

D1008 55, 66 Obsolete

. Used with T874D1082, F1056; used in

Q674D1040 Y594D1057.

D1016 55 Obsolete

D1032 58 Obsolete. Borg-Warner; used with T874G. T874D1165/

. Carrier part no. HH93AZ170; RC-RH jumper. Q674D1040 RC-RH jumper required.

Wiring differences (old=new):

Q674D1040

Y=Y2, O=Y1, W=W2; jumper W1-Y2 required.

D1040 55 TRADELINE Q674D1040

D1057 55, 66 Obsolete

Both the thermostat and subbase must be replaced.

. York part no. 2TB04700424A. Q674D1040

75 60-2485—8

Page 76

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 9. Q674 Subbase Cross Reference.

Model

Number

D1065 63 Obsolete. Includes two LEDs; used with T874F1122. T874F1015/

D1099 55, 66 Obsolete

D1107 55, 66 Obsolete. Snyder General part nos. 654958801/

Fig. No. Description

. Trane part no. BAS-0430; used with T874A-F. Q674D1040

Q674 Trade

Replacement Remarks

Replacement has no LEDs.

Q674D1040

Q674F1040.

1520503/ 4ELN30070.

D1115 208 Trol-A-Temp; used with T874D1801. None See Trol-A-Temp.

D1123 208 Trol-A-Temp; gray color; used with T874D1827. None See Trol-A-Temp.

D1156 55 Obsolete

. Gray color; includes removable jumper

Q674D1040 Replacement is beige color.

between RC and RH terminals.

D1164 66 Obsolete

. Carrier part no. HH93AZ211; used in

Q674D1040

Y594D1440.

D1172 208 Obsolete

. Amana logo; part no. P121501F; removable

Q674D1040

jumpers between RC and RH terminals.

D1180 55 Obsolete

D1198 55, 66 Obsolete. Standard OEM. T874D1165/

. York logo; part no. 2TH04703224A. Q674D1040

Replacement is beige color.

Q674D1040

Q674E System: OFF-HEAT-AUTO-COOL; Fan: AUTO-ON

E1007 82 Used with T874D1504; used in Y594D1180. Q674E1049

E1015 84 Obsolete. Lennox heat pump; used with T874G1006,

G1154.

Y594G1252

Wiring differences (old=new): R=O, M=Y, F=G, V=R, Y=W2; E-W2 jumper required.

E1049 193 TRADELINE; used with T874D2031 and TG504A1025;

Q674E1049

used in Y594D1354.

E1056 82 Obsolete. Amana part no. D68535-7; used with

Q674E1049 RC-RH jumper required.

T874C1059, C1331; used in Y594C1009.

E1064 83 Obsolete

E1072 82 Carrier part no. HH93AZ176; RC-RH jumpered

. RC-RH jumpered internally; EM HEAT LED. Q674E1049

Q674E1049 RC-RH jumper required.

internally.

E1080 82 Trane part no. BAY28X184. Q674E1049

E1098 85 Obsolete. Used with T874A-D. Q674E1049 RC-RH jumper required.

E1106 185 Obsolete

. ITT Nesbitt. See OEM for

replacement.

E1114 87 Carrier part no. HH93AZ177; RC-RH jumper;

LOCKOUT LED to indicate compressor lockout; used

Q674E1049 RC-RH jumper required;

replacement has no LED.

with HH07AT series thermostats.

E1122 83 Obsolete

. Square D part no. 63600-002-10; CHECK

Q674E1049 Replacement has no LED.

LED.

E1148 86 Obsolete

G1022.

. Lennox heat pump; used with T874G1014,

Y594G1252

Wiring differences (old=new): R=O, M=Y, F=G, Y=W2, V-VR=R; must use single transformer.

E1155 88 Obsolete

. Lennox part no. 91C7501; HIGH and LOW

Q674E1049 Replacement has no LEDs.

LEDs; used with T874B1076, D1017.

E1197 89 Obsolete

with T874D1116.

. McQuay part no. 02005961; two LEDs; used

Q674E1049 Wiring differences (old=new):

D=O; replacement has no LEDs.

E1205 80 Obsolete

. Fedders special; SERVICE LED; used with

Q674E1049 Replacement has no LEDs.

T874D1462.

E1213 82 York part no. 2TB04700224A. Q674E1403

E1221 82 Heil Quaker part no. HQ712003HW. Q674E1049

Both the thermostat and subbase must be replaced.

60-2485—8 76

Page 77

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 9. Q674 Subbase Cross Reference.

Model

Number

Fig.

No. Description

Q674 Trade

Replacement Remarks

E1262 82 Lennox part no. 13F1701. Q674E1049

E1270 198 Obsolete. Carrier part no. HH93AZ189; used with

Y594G1419

E-W2 jumper required.

T874L1000 (HH07AT176).

E1304 82 Obsolete

. BDP part no. P272-1887; used with

Y594G1419

E-W2 jumper required.

T874L1026.

E1312 224 Obsolete

. McQuay part no. 60684901; one LED; used

Q674E1049 Replacement has no LEDs. with T874A1523, A1549, D1686, D1918.

E1320 82 Obsolete

E1338 88 Obsolete

. Trane part no. BAS-0434. Q674E1049

. Goodman part no. CHTS36-60; HIGH and

Q674E1049 Replacement has no LEDs. LOW LEDs; used with T874B1100; used in Y594B1042.

E1346 82 Obsolete

. Snyder General part nos. 1505753/1506753/

Q674E1049 654958B02; used with T874D1769; used in Y594D1297.

E1353 210 Obsolete. Mammoth; used with T874Y1005; used in

T8611M2025

Y594Y1004.

E1379 212 Trol-A-Temp by Honeywell; used with T874A1465. None See Trol-A-Temp.

E1395 222 Obsolete. Carrier part no. HH93AZ209; used with

T874B1134 (HH07AT199).

T874B1019/

Q674E1049

Wiring differences (old=new):

W1 =W; RC-RH jumper required; replacement has no LEDs.

E1403 82 TRADELINE; designed to replace York 2TH04701024;

Y594D1347

used with T874D1942; used in Y594D1347.

E1411 82 Obsolete. Carrier Canada part no. HH93AZ176-W;

gray color; removable jumper between RC and RH

Q674E1049 RC-RH jumper required.

Replacement is beige color.

terminals.

E1429 87 Carrier Canada part no. HH93AZ177-W; gray color;

includes LOCKOUT LED; removable jumper between RC and RH terminals.

E1445 82 Obsolete

. Carrier part no. HH93AZ217-W; gray color;

removable jumper between RC and RH terminals.

Q674E1049 RC-RH jumper required.

Replacement has no LOCKOUT LED and is beige color.

Q674E1049 RC-RH jumper required.

Replacement is beige color.

E1460 224 McQuay logo; part no. 073319801; includes one LED.

E1478 82 Obsolete. Armstrong logo; part no. 03299A19. Q674E1049 RC-R jumper required.

Replacement is beige color.

E1486 82 Obsolete

. Standard OEM. Q674E1049 RC-R jumper required.

Replacement is beige color.

Q674F System: EM.HT.-HEAT-AUTO-COOL-OFF;

Fan: AUTO-ON

F1006 141 Obsolete

. Includes EM HEAT LED; used with

Q674F1022 Jumper E-X2.

T874C1331.

F1022 142 Includes LED and field selectable inserts; used with

Q674F1022

T874C1059; used in Y594C1017, C1330.

F1030 146 Carrier part no. HH93AZ174; SUPL HEAT LED; used

with T874D1074 (HH07AT172).

F1048 149 Obsolete. Includes EM HEAT LED and auxiliary power

terminal Z.

Q674F1022 Wiring differences (old=new):

C=X1, X=X2.

Q674F1022 Replacement does not include

Z terminal and only requires one transformer.

F1063 146 Obsolete

LED; used with T874D1074 (HH07AT172).

F1071 142 Obsolete

. Carrier part no. HH93AZ181; SUPL HEAT

. Square D part no. 63600-002-11; CHECK

Q674F1022 Wiring differences (old=new):

C=X1, X=X2.

Q674F1022

LED.

Both the thermostat and subbase must be replaced.

77 60-2485—8

Page 78

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 9. Q674 Subbase Cross Reference.

Model

Number

F1089 152 Obsolete. Includes EM HEAT LED; X2-E and RC-RH

Fig. No. Description

Q674 Trade

Replacement Remarks

Q674F1022

jumpers.

F1097 142 Obsolete

F1105 145 Obsolete. Lennox heat pump; EM HEAT LED; used

. Southwest special; W2-X2 jumper. Q674F1022

Y594G1252

with T874G1154.

F1113 1 50 Obsolete . Lennox heat pump; part no. 24F6201; V-VR

Y59461252 jumper; EM HEAT LED; changeover in cooling; used with T874G1014, G1022.

F1121 153 Obsolete

. Westinghouse heat pump; EM HEAT LED;

Y594G1252

used with T874G1048.

F1139 148 Obsolete. Tappan heat pump; EM HEAT LED; auto fan

Y594G1252

in emergency heat mode; used with T874G1147.

F1162 151 Obsolete

. Crispaire heat pump; EM HEAT LED; used

Y594G1393

with T874G.

F1170 153 Obsolete. Heatwave (Southwest Mfg.) heat pump; EM

Y594G1252

HT LED; used with T874G1105.

F1188 153 Obsolete. Luxaire heat pump.

F1196 178 Obsolete. Williamson; EM HEAT and SERVICE LEDs;

Y594G1252

Q674F1220 used with T874N1008; used in Y594N1007.

F1204 154 Obsolete

. Special for Crispaire; EM HEAT and COMP

Y594G1393

FAULT LEDs; used with T874G1089; used in Y594G1153.

F1212 155 Includes AUX HEAT and EM HEAT LEDs; used with

T874G1246, G1451, G1592, G1915; used in

Q674F1212 or

Y594G1252

Y594G1252.

F1220 178 Used with T874N1016; used in Y594N. Q674F1220

F1238 155 Obsolete

. Rheem part no. 41-20797-14; AUX HEAT

Y594G1252 and EM HEAT LEDs; used with T874G1097, G1212, G1220, G1238.

F1246 156 Obsolete. Westinghouse heat pump; EM HEAT and

Y594G1252 AUX HEAT LEDs; auto fan in emergency heat mode; changeover in cooling mode.

F1253 157 Obsolete. Wesco/Addison heat pump; used with

Y594G1252 T874G1261, G1279, G1287.

F1261 179 Includes two LEDs; used with T874N1024; used in

Y594G1419 Y594N.

F1279 158 Obsolete

. Westinghouse heat pump; two LEDs; used

Y594G1252 with T874G.

F1295 147 Obsolete

. Keeprite/Westinghouse heat pump;

Y594G1252 SERVICE, AUX HEAT and EM HEAT LEDs; used with T874G1188.

F1311 155 York heat pump; AUX HEAT and EM HEAT LEDs; used

Y594G1252 with T874G1410.

F1329 142 Obsolete. Heil Quaker part no. HQ712005HW; one

Q674F1022

LED and field selectable inserts.

F1337 166 Obsolete

. WeatherKing heat pump; two LEDs and field

Q674F1022 Wiring differences (old=new): selectable inserts; used with T874D1009; used in Y594D1222.

F1345 194 Obsolete

. Addison heat pump; EM HEAT and CHECK

Y594G1252

LEDs; used with T874G; used in Y594G.

Both the thermostat and subbase must be replaced.

Wiring differences (old=new): V=R, Y=W2, F=G, X2=X, R=O, M=Y; L-E jumper required.

Wiring differences (old=new): R=O, M=Y, F=G, Y=WC, V=VR=R; must use single transformer.

Wiring differences (old=new): C=X.

Wiring differences (old=new): A=L.

Wiring differences (old=new): Y1=O, C=X, W1=Y, X=L.

Wiring differences (old=new): L=X2, Y=Y1.

Wiring differences (old=new): L1=L.

Wiring differences (old=new): S=L; replacement does not include A or T terminals.

R=RC-RH; replacement has no LEDs.

Wiring differences (old=new): Y1=O, C=X, W1=Y, X=L.

60-2485—8 78

Page 79

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 9. Q674 Subbase Cross Reference.

Model

Number

Fig.

No. Description

F1360 167 Obsolete. Rheem part no. 41-20797-17; AUX HEAT

and EM HEAT LEDs; used with T874G1493.

F1378 195 Obsolete. Includes EM HEAT and AUX HEAT LEDs;

used with T874G1501.

F1394 139 Obsolete

. Nepco heat pump; HEAT PUMP and AUX HEAT LEDs; System: AUX HEAT-HEAT PUMP-2 STAGE HEAT-OFF-COOL; used with T874D1595.

F1402 169 Obsolete

. Coleman heat pump; two LEDs; used with T874G1576; used in Y594G1377.

F1410 170 Used with T874G1246, G1915; used in Y594G1393.

F1428 199 Obsolete. Used with T874G1600; used in Y594G1401.

F1436 167 Includes AUX HEAT and EM HEAT LEDs; changeover

in heating mode; used with T874G1626; used in Y594G1526.

F1444 227 Includes AUX HEAT, EM HEAT and CHECK LEDs;

used with T874G1642; used in Y594G1419.

F1451 204 Obsolete

. York part no. 2TB047700524A; one LED and field selectable inserts.

F1477 227 TRADELINE; gray color; used with T874G1741,

G1824; used in Y594G1476, G1534.

F1485 211 Trol-A-Temp by Honeywell; changeover is provided by

Trol-A-Temp zone panel; used with T874G1758; used in Y594G1492.

F1501 223 Obsolete. Carrier two-speed compressor heat pump;

used with T874S1001.

F1519 231 Obsolete

. Nordyne; used with T874G1832, G1840; used in Y594G1542, G1559.

F1535 229 Obsolete

. Lennox heat pump; gray color; used with T874G1857; used in Y594G1583.

F1543 204 Obsolete

F1550 243 Obsolete

. TRADELINE Q674F1022 Wiring differences (old=new):

. Amana part no. 10573901; includes two LEDs; used with T874G1899; used in Y594G1591.

F1568 155 Obsolete

. Gray color; includes two LEDs; used with only T874G1931.

F1584 169 TRADELINE; includes two LEDs; used with

T874G1972; used in Y594G1633. Direct replacement for Coleman/Evcon Y594G1377 (T874G1576/ Q674D1402); Coleman part no. 3600-373.

F1592 238 Heat Controller; Fan: AUTO-ON; System: AUX HEAT-

HEAT PUMP- 2 STAGE HEAT-OFF-COOL; includes two LEDs; used with T874C1844; used in Y594C1413.

F1600 169 Obsolete

. Amana part no. 10573903; includes two LEDs; used with T874G1980; used in Y594G1641.

F1634 139 Standard OEM; System: AUX HEAT-HEAT PUMP-

2 STG HEAT-OFF-COOL; includes two LEDs; used with T874D2155.

F1667 155 WaterFurnace logo; part no. TA21H03; System: OFF-

AUTO-HEAT-EM HT; includes two LEDs; used with T874G2046.

Both the thermostat and subbase must be replaced.

Q674 Trade

Replacement Remarks

Y594G1526

Y594G1252

Wiring differences (old=new): L1=L; changeover in cooling only.

T874D1165/

Q674B1018

Replacement has HEAT-OFF-

COOL system switching and no LEDs.

Y594G1633

Y594G1393

Y594G1419

Wiring differences (old=new): jumper W1-Y1.

None

Y594G1419

Q674F1012 Wiring differences (old=new):

X2=X; X1=B.

Y594G1476

None See Trol-A-Temp.

T8611M2025

Includes night setback.

(programmable)

Y594G1252

Replacement has auto changeover in cooling mode only.

Y594G1161

Wiring differences (old=new): E=X2, C=B, L=F.

X2=X, X1=B.

Y594G1633

Y594G1476 Y1-W1 jumper required.

Y594G1633

Y594R1425 E-W2 jumper required; system

switch: EM.HT.-HEAT-OFFCOOL.

Y594G1633 Wiring differences (old=new);

W3=W2.

Y594G1716

79 60-2485—8

Page 80

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 9. Q674 Subbase Cross Reference.

Model

Number

F1675 248 Obsolete. WaterFurnace logo; part no. TA21H03;

Fig. No. Description

includes four LEDs.

Q674 Trade

Replacement Remarks

See OEM for replacement.

Q674G System: OFF-AUTO; Fan: None

G1005 184 Obsolete

G1013 186 Obsolete

. Used in Y594F1063. Q674G1070

. Climate Control; used with T874D1298. See OEM for

replacement.

G1021 91 Obsolete

. Includes O and B terminals; used with

Q674G1070

T874A-F,Q or T874D1082; used in Y594D1032.

G1047 92 Obsolete

G1054 188 Obsolete. Singer part no. 0200-5963; used with

T874D1298.

G1062 232 Obsolete

. Used with T874C1018, C1125. T8611

See OEM for replacement.

. Singer; used with T874D1298. See OEM for

replacement.

G1070 91 TRADELINE Q674G1070

G1088 92 Obsolete. LSI-Mammoth part no. 71120201; used with

T874C.

G1096 90 Obsolete

. Climate Control part no. 02005958; used

with T874D1439, D1447.

G1104 94 Obsolete

. McQuay part no. 0200-5963; two LEDs;

used with T874D1116.

G1120 202,

G1138 91 Obsolete

G1153 184 Obsolete

Obsolete

226

LEDs; no fan switching; used with T874D1694, G1926.

. McQuay part no. 60684701; two SERVICE

. Trane part no. BAS-0433; used with T874A-F. Q674G1070

. Carrier part no. HH93AZ212; used in

See OEM for replacement.

Q674G1070

Y594D1396.

G1161 184 Gray color. Q674G1070 Replacement is beige color.

G1179 202 Obsolete

. McQuay logo; part no. 073319601; includes

Q674G1161 Replacement has no LEDs.

two LEDs.

Q674J System: EM.HT.-AUTO-OFF; Fan: AUTO-ON

J1001 180 Obsolete. Singer heat pump part no. 02005964; EM

HEAT LED; changeover heat mode.

J1019 159 Obsolete

. Westinghouse heat pump; EM HT LED;

System: EM.HT.-ON-OFF; used with T874G1048.

J1027 160 Obsolete

. York part no. 025-22291; EM HEAT LED;

See OEM for replacement.

Y594G1252

Y594G1567

Wiring differences (old=new): W=W2.

auto fan in emergency heat mode; changeover in cool mode; used with T874G1170, G1196, G1428, G1345, G1444; used in Y594G1013, G1138, G1229.

J1035 161 Carrier heat pump; part no. HH93AZ173; System:

Y594G1674

SUPL.HT.-ON-OFF; SUPL HEAT LED; used with T874G1055 (HH07AT171).

J1043 162 TRADELINE heat pump model; designed for use on

Trane heat pumps; AUX HT and EM HT LEDs; auto fan

Q674J1043 or

Y594G1161

Designed for use on Trane

heat pumps. in emergency heat; changeover in cooling mode; used with T874G1204 and C815A1008; used in Y594G1161.

J1050 183 Obsolete

. Westinghouse heat pump; EM HEAT and

Y594G1674

AUX HEAT LEDs; used with T874G1071.

J1068 144 Obsolete. Carrier heat pump; part no. HH93AZ183;

Y594J1019 used with T874J1002 (HH07AT175) or T874J1028 (HH07AT165).

J1076 180 Obsolete

. McQuay part no. 02005964; two LEDs; used

Q674F1022 Replacement has no LEDs.

with T874A,D.

Both the thermostat and subbase must be replaced.

60-2485—8 80

Page 81

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 9. Q674 Subbase Cross Reference.

Model

Number

Fig.

No. Description

J1084 171 Obsolete. BDP heat pump; part no. 34427DP126,

P272-1879; EM HEAT LED; used with T874J1010.

J1118 196 Obsolete

. Carrier heat pump; part no. HH93AZ188; SUPL HEAT LED; System: SUPL.HT.-ON-OFF; used with T874G1055 (HH07AT171).

J1126 160 Obsolete

. Luxaire no. 026-00068-000; EM HEAT LED; used with T874G1568; used in Y594G1351.

J1142 174 Obsolete. American Standard part no. WY28X0250;

AUX HEAT and EM HEAT LEDs; used with T874G1675; used in Y594G1443.

J1159 206 Obsolete. Carrier heat pump; part no. HH93AZ196;

used with T874J1002 (HH07AT175) or T874J1028 (HH07AT165).

J1167 175 Obsolete

. Carrier heat pump; MANUAL, AUTO, HEAT PUMP and DEFROST LEDs; System: SUPL HEATON-OFF; used with T874G1717; used in Y507J1201.

J1175 216 Obsolete

. Snyder General part nos. 1505756, 1506756; CHECK, AUX HEAT and SYSTEM LEDs; used with T874G1774, G1782; used in Y594G1500, G1518.

J1191 161 Obsolete

. Carrier heat pump; gray color; used with T874G1790.

J1209 160 TRADELINE; designed to replace Y594G1013 (York

part no. 2TH11702424), Y594G1229 (York part no. 6TH11702424) and York part no. 2TH11704124; used with T874G1865; used in Y594G1567.

J1217 171 Obsolete. Nordyne part no. 9132250; used with

T874J1036, J1044.

J1225 160 Obsolete

. TRADELINE; gray color; designed to replace Y594G1013 (York part no. 2TH11702424), Y594G1229 (York part no. 6TH11702424) and York part no. 2TH11704124; used with T874G1873; used in Y594G1575.

J1241 144 Obsolete. Carrier Canada part no. HH93AZ183-W;

gray color; System: SUPL HT-ON-OFF; includes one LED.

J1258 161 Obsolete

. Carrier Canada part no. HH93AZ173-W; gray color; System: SUPL HT-ON-OFF; includes one LED.

J1266 160 York Canada; gray color; includes EM HT LED; used in

Y594G1625.

J1274 161 TRADELINE; System: SUPL HT-ON-OFF; includes

one LED; used with T874G2004; used in Y594G1674.

J1282 244 Obsolete

. TRADELINE; System: SUPL HT-ON-OFF; includes SUPL HT LED; used with T874J1069; used in Y594J1019.

Q674K System: OFF-HEAT-AUTO-COOL; Fan: None

K1000 93 Obsolete

K1018 95 Obsolete

. Carrier part no. HH93AZ172; RC-RH jumper. Q674E1049 Fan switch is not operational.

. Oneida Heater part no. 3040284-02; System: OFF-WOOD-WOOD/OIL-OIL; used with T874F1106.

Both the thermostat and subbase must be replaced.

Q674 Trade

Replacement Remarks

Y594J1019 Wiring differences (old=new):

W1=W2, F=L.

Y594G1674 Wiring differences (old=new):

C=X;Y1=W1; jumper required; no auto fan in emergency heat.

Y594G1567

Y594G1161

Y594J1019

Y594G1252

Wiring differences (old=new): C=X, D=L; replacement has AUX HEAT and EM HEAT LEDs.

Y594G1252

Wiring differences (old=new): E=W2, W1=W3, X=E, C=X.

Y594G1252

Wiring differences (old=new): C=X; replacement has °F scaleplate.

Y594G1567

Y594J1019 Wiring differences (old=new):

F=L.

Y594G1567

Replacement is beige.

See OEM for replacement.

Y594G1674

Y594G1567

Replacement is beige color.

Y594G1674

(Recontrol)

T8511G1021

Q674K1026

81 60-2485—8

Page 82

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 9. Q674 Subbase Cross Reference.

Model

Number

Fig. No. Description

K1026 95 System: OFF-WOOD-WOOD/ OIL-OIL; used with

T874F1155.

K1034 93 Obsolete

. Snyder General part no. 4ELN-7920. Q674E1049 Fan switch is not operational.

K1042 93 Obsolete. Carrier part no. HH93AZ172-W; gray color;

includes removable jumper between RC and RH terminals.

Q674L System: EM.HT.-HEAT-OFF-COOL; Fan: ON-AUTO

L1017 101 Obsolete

. York heat pump; EM HEAT LED; cooling mode changeover; compressor lockout; auto fan in EM.HT; used with T874R1046.

L1025 102 Obsolete. Lennox heat pump; part no. 24F6101; EM.

HEAT LED; V-VR jumper; used with T874R1020, J1038.

L1033 115 Obsolete

. Rheem heat pump; EM HEAT LED; used with T874R1152.

L1041 103 Obsolete. Carrier heat pump; part no. HH93AZ175;

SUPL HEAT LED; used with T874G1055 (HH07AT171), G1071 (HH93AZ175), G1113.

L1066 122 Obsolete

. Fedders heat pump; used with T874R1269; used in Y594R1037.

L1074 124 Obsolete

. Carrier heat pump; part no. HH93AZ186; SUPL HT LED; used with T874J1002 (HH07AT175) or T874J1028 (HH07AT165).

L1082 104 Obsolete. Crispaire heat pump; W2-H jumper; EM

HEAT LED; used with T874R1061, R1111.

L1090 105 Obsolete

. Fedders heat pump; EM HEAT LED; changeover in heat mode; used with T874C1398, C1406, C1414.

L1108 106 Obsolete

. Westinghouse; EM HEAT LED.

L1116 107 Obsolete. Carrier part no. HH93AZ171; SUPL HEAT

LED; used with T874D1264 (HH07AT173).

L1132 108 Heil Quaker part no. HQ711598; used with T874R1137,

R1673, R1731, R1749, R1814; used in Y594R1110, R1466, R1524, R1532, R1607.

L1140 109 Obsolete. Includes EM HEAT and AUX HEAT LEDs;

used with T874R1053; used in Y594G1136.

L1157 115 Obsolete

. Rheem part no. 41-20796-14; EM HEAT and AUX HEAT LEDs; used with T874R.

121 Obsolete. Used with T874C.

123 Obsolete. Used with T874R.

L1165 110 Obsolete. Lennox no. 24F5901; factory installed V-VR

jumper; EM HEAT and SERVICE LEDs; stage 2 heat is isolated; used with T874C1448, R1178 and C815A1013.

L1173 112 Obsolete

. Westinghouse; AUX HEAT and EM HEAT LEDs.

L1181 113 Used with T874R1129; used in Y594R.

Both the thermostat and subbase must be replaced.

Q674 Trade

Replacement Remarks

Q674K1026

Q674E1049 Fan switch is not operational.

Y594R1243

Wiring differences (old=new): W=W2, X=L, B=X.

Y594R1243

Wiring differences (old=new): M=Y, F=G, V-VR=VR, Y=W2, R=O.

Y594R1243

Y594G1419 Wiring differences (old=new):

C=X, jumper Y1=W1.

Y594R1615

Wiring differences (old=new): K=E, C=X, W1=B, Z=L.

Y594J1001

Y594R1243

Replacement has auto fan in emergency heat mode.

Y594R1425

Wiring differences (old=new): K=E, C=X.

Y594R1243

See OEM for replacement.

Y594R1292

Y594R1763

Designed for use on Trane heat pumps.

Q674L1207

Y594C1322

Y594R1243

Y594R1763

Wiring differences (old=new): V-VR=R, M=Y, F=G, X=B, Y=W, A=T, R=O, E=X2.

Y594R1243

Wiring differences (old=new): X1=X.

60-2485—8 82

Page 83

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 9. Q674 Subbase Cross Reference.

Model

Number

Fig.

No. Description

L1199 114 Obsolete. Lennox no. 24F6001; used with T874D1207

and C815A1013.

L1207 115 Used with T874R1152, R1590, R1640, R1921; used in

Y594R1243, R1706.

L1215 116 Obsolete. Crispaire heat pump; used with T874R1111;

used in Y594R1128.

L1223 117 Obsolete

L1231 182 Obsolete

. Westinghouse special. See OEM for

. Used with T874R1186 and W89. None

L1249 115 Obsolete. Used with T874R1194 and W89.

L1256 118 Obsolete. Westinghouse special; used with

T874W1007.

L1264 119 Obsolete

. Intertherm heat pump; EM HEAT and SERV LEDs; used with T874R1202, R1608, R1699; used in Y594R1185, R1409, R1482.

L1272 120 Obsolete

. York part no. 025-22290; used with T874R1046, R1145; used in Y594R1011, R1102; used with T874R1228, R1251 R1327 and C815A1039; used in Y594R1144, R1151, R1193.

L1280 233 Obsolete. Lennox no. 52C7601; used with T874W1023

and W89.

L1298 182 Obsolete. Singer heat pump; used with T874R1160

and W89.

L1314 115 Obsolete

. Westinghouse heat pump; used with T874R1244 and W89.

L1322 127 Obsolete. EM HEAT and AUX HEAT LEDs; used with

T874C1455.

L1330 120 Obsolete. York heat pump; used with T874R.

L1348 115 Obsolete

. Williamson heat pump; used with T874R1236.

L1355 111,

190

Obsolete used with T874C1448, R1178 and C815A1015.

. Lennox part no. 31F3201; V-VR jumper;

L1363 129 Obsolete. York heat pump; EM HEAT LED; used with

T874G1402.

L1371 124 Obsolete

. BDP heat pump; part no. 34427DP125, P272-1878; EM HEAT LED; used with T874J1010.

L1389 114 Obsolete

. Lennox part no. 41F6501; V-VR jumper; used with T874D1207.

L1397 103 Obsolete

. Carrier part no. HH93AZ185A; SUPL HEAT LED.

Both the thermostat and subbase must be replaced.

Q674 Trade

Replacement Remarks

T8611M2025

(programmable)

Wiring differences (old=new): V-VR=R, Y=W3, X=C, R=O, M=Y, M2=Y2-W2, F=G; jumper Y2-W2; no outdoor reset needed; use only one system transformer.

Q674L1207 or

Y594R1243

Replacement has auto fan in emergency heat mode. Wiring differences (old=new): A=L; set anticipator to 1.2.

replacement.

Y594R1243

T8611M2025

Includes night setback.

(programmable)

Y594R1672

Y594R1763

Wiring differences (old=new):

W2=W, X=B, Z=no connection, K=X, W1=H.

Y594R1672

Y594W1014

See OEM for replacement.

Q674L1207 or

Y594R1243

Y594R1664

Wiring differences (old=new): L=X, X=B.

Q674L1207

Y594R1763

Wiring differences (old=new): V-VR=R, M=Y, F=G, X=B, Y=W, A=T, R=O, E=X2.

Y594R1425

Wiring differences (old=new): W=W2, X=E, B=X; jumper YW1.

Y594J1001 Wiring differences (old=new):

W1=W2, F=L.

T8611M2025

(programmable)

Wiring differences (old=new): V-VR=R, Y=W3, X=C, R=O, M=Y, M2=Y2-W2, F=G; jumper Y2-W2; no outdoor reset needed; use only one system transformer.

Y594G1393

Wiring differences (old=new): C=X.

83 60-2485—8

Page 84

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 9. Q674 Subbase Cross Reference.

Model

Number

Fig. No. Description

L1405 106 Obsolete. BDP heat pump; part no. HH641501; used

with T874R1335; used in Y594R1201.

L1413 133 Obsolete. Fedders heat pump; used with T874R1343;

used in Y594R1219.

L1421 125 Obsolete

. Coleman heat pump; used with T874R1368;

used in Y594R1235.

L1439 131 Obsolete. Carrier part no. HH93AZ187; SUPL HEAT

LED; System: SUPL HT-HEAT- COOL; used with T874R1384 (HH07AQ170).

L1447 128 Obsolete. Williamson heat pump; three LEDs; used

with T874R1392; used in Y594R1250.

L1454 131 Obsolete

. Carrier part no. HH93AZ197; SUPL HEAT

LED; used with T874R1384 (HH07AQ170).

L1462 113 Obsolete

. LSI heat pump; part no. 104710002; used

with T874R1400.

L1496 136 Obsolete

. Trane heat pump; used with T874R1426;

used in Y594R1284.

L1504 134 Rheem part no. 41-20796-24; used with T874R1442,

R1434, R1459; used in Y594R1631, R1649, R1854.

L1512 108 Includes two LEDs; used with T874R1467; used in

Y594R1292.

L1520 123 Includes EM HEAT and AUX HEAT LEDs; used with

T874R1475; used in Y594R1300.

L1538 130 Obsolete. Snyder General heat pump; used with

T874R1483, R1517, R1566 and C815A1005; used in Y594R1318, R1342, R1375.

132 Obsolete. Used with T874R1574, R1582; used in

Y594R1383, R1391.

L1546 140 Obsolete

. Rheem part no. 41-20797-21; three LEDs; used with T874W1031 and C815A1005; used in Y594W1022.

L1553 137 Obsolete

. Includes three LEDs; used with T874R1491; used in Y594R1326.

L1561 121 Obsolete. Used with T874C1638; used in Y594C1322.

123 Obsolete

L1579 135 Obsolete

. Used with T874R.

. Carrier heat pump; part no. HH93AZ198; SUPL HEAT LED; used with T874R1384 (HH07AQ170).

L1587 168 Used with T874R1616; used in Y594R1425.

L1595 200,

Obsolete. Miller heat pump; used with T874R1624 or

201

T874R1202; used in Y594R1433.

L1603 134 Obsolete. Used with T874R1632.

L1611 136 Obsolete. American Standard heat pump; part no.

WY28X235; used with T874R1657; used in Y594R1441.

L1637 207 Obsolete. Carrier heat pump; part no. HH93AZ195;

used with T874J1002 (HH07AT175) or T874J1010 (HH07AT165).

Both the thermostat and subbase must be replaced.

Q674 Trade

Replacement Remarks

Y594R1243

Y594R1425

Wiring differences (old=new): K=E, C=X, Z=L; remove W1-Y jumper.

Y594R1797

Q674L1207 or

Y594G1393

Y594R1425

Wiring differences (old=new):

C=X.

Wiring differences (old=new): A=L.

Y594R1393

Wiring differences (old=new): C=X.

Y594R1243

Wiring differences (old=new): X1=X.

Y594R1763

Y594R1300

Y594R1292

Y594R1300

Y594R1763

Wiring differences (old=new): C=B, W1=W, E=X2, X=F.

Y594R1243

Wiring differences (old=new): C=X, X=L, W=W2.

T8611M2025

Includes night setback.

(programmable)

Y594R1615

Y594C1322

Use Y594C1322 when T874C is used.

Y594R1243

Use Y594R1243 when T874R is used.

Y594R1243

Wiring differences (old=new): C=X.

Y594R1425

Y594R1243

Y594R1763

Y594R1243

Y594R1763

Y594J1001

60-2485—8 84

Page 85

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 9. Q674 Subbase Cross Reference.

Model

Number

L1678 209 Trol-A-Temp by Honeywell; gray color; used with

Fig.

No. Description

Q674 Trade

Replacement Remarks

None See Trol-A-Temp.

T874R1707; used in Y594R1490.

L1686 209 Trol-A-Temp by Honeywell; used with T874R1715;

None See Trol-A-Temp.

used in Y594R1508.

L1702 132 Obsolete. Snyder General heat pump; part no.

Y594R1672 654958B07; used with T874R1723 and C815A1005; used in Y594R1516.

L1710 230 Used with T874R1822; used in Y594R1615.

L1728 228 Obsolete. Lennox; gray color; used with T874R1855;

Y594R1615

Y594R1763 used in Y594R1714.

L1736 120 Designed to replace Y594R1011 (York part no.

Y594R1664 2TH11702224); used with T874R1871; used in Y594R1664.

Designed to replace Y594R1151 (York part no.

Y594R1672 2TH11702324), Y594R1193 (York part no. 6TH11702224) and York part no. 2TH11704024; used with T874R1889 and C815A1054; used in Y594R1672.

L1751 230 Gray color; used with T874R1897, used in

Y594R1680 Y594R1680.

L1769 124 Obsolete. Nordyne part no. 9132260; used with T874J. See OEM for

replacement.

L1777 120 Obsolete

. Gray color; designed to replace Y594R1151

Y594R1672 (York part no. 2TH11702324), Y594R1193 (York part no. 6TH11702224) and York part no. 2TH11704024; used with T874R1905 and C815A1059; used in Y594R1698.

Designed to replace Y594R1011 (York part no.

Y594R1664 2TH11702224); used with T874R1913; used in Y594R1706.

L1785 103 Obsolete

. Carrier part no. HH93AZ175-W; Canada;

Y594G1476 gray color; System: Supl Ht-Heat-Off-Cool; includes one LED.

L1793 124 Obsolete. Carrier Canada part no. HH93AZ186-W;

Y594J1019 gray color; Fan: Auto-On; System: Supl Ht-Heat-OffCool; includes one LED.

L1801 197 American Standard (Trane) part no. THT1225; includes

Y594R1763

two LEDs; used with T874R1939; used in Y594R1748.

L1819 168 Obsolete. Inter-City Products part no. HQ1149407HW;

Y594R1425 includes three LEDs; used with T874R1947; used in Y594R1755.

L1827 197 TRADELINE; includes two LEDs; used with

Y594R1763 T874R1954; used in Y594R1763; direct replacement for Trane/American Standard Y594R1748 (T874R1939/Q674L1801) Trane part no. ASYSTAT 631A, Y594R1136 (T874R1053/Q674L1140).

L1835 140 Obsolete. Inter-City Products; includes three LEDs;

used in Y594W1030.

L1843 115 Obsolete

. Consolidated Industries part no. 9036100;

T8611M2025

(programmable)

Y594R1680 gray color; includes two LEDs; used with T874R1962; used in Y594R1771.

L1850 120 York Canada; gray color; includes one LED; used with

Y594R1672 T874R1970; used in Y594R1789.

Both the thermostat and subbase must be replaced.

Wiring differences (old=new): C=B, W1=W, X=X2.

Wiring differences (old=new): Y1=Y, L=F, W1=W, E=X2, C=B.

Replacement is beige.

Wiring differences (old=new): C=X; Y1-W1 jumper required.

Includes night setback.

Includes CHECK LED.

85 60-2485—8

Page 86

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 9. Q674 Subbase Cross Reference.

Model

Number

Fig. No. Description

Replacement Remarks

L1868 125 TRADELINE; includes two LEDs; used with

T874R1988; used in Y594R1797; direct replacement for Evcon/Coleman Y594R1235 (T874R1368/ Q674L1421) Coleman part no. 3600-368.

L1876 245 Obsolete. Amana part no. 10573902; includes two

LEDs; used with T874R2002; used in Y594R1805.

L1884 245 Obsolete

. Amana part no. 10573904; includes two

LEDs; used with T874R2010; used in Y594R1813.

L1892 103 Obsolete

. TRADELINE; System: SUPL HT-HEATOFF-COOL; includes one LED; used with T874G2004; used in Y594G1666; direct replacement for Carrier Y507J1011 (T874G1055/Q674L1041) Carrier part no. HH07AT171/HH93AZ175.

L1900 241 Obsolete

. TRADELINE; System: SUPL HT-HEATOFF-COOL; includes SUPL HT LED; used with T874J1069; used in Y594J1001; direct replacement for Carrier T874J1028/Q674J1068 (Carrier part no. HH07AT165/HH93AZ183), Carrier T874J1002/ Q674J1068 (Carrier part no. HH07AT175/ HH93AZ183).

L1918 125 Obsolete

. York logo; part no. 2TH11703424A; includes two LEDs; used with T874R2028 in Y594R1821.

L1934 123 Obsolete. Addison logo; part no. 843-277; includes

T8611M2025

three LEDs; used with T874W1106 in Y594W1055.

Q674N System: OFF-HEAT-COOL-EVAP; Fan: AUTO-ON

N1015 60 Obsolete

evaporative cooler circuit; used with T874C1182.

N1023 61 Obsolete

used with T874C1349.

. Goettl heat pump; changeover in heat mode;

. Sigler heat pump; evaporative cooler circuit;

See OEM for replacement.

Q674P System: SUPL HT-HEAT-COOL; Fan: AUTO-ON

P1005 126 Obsolete. Carrier heat pump; part no. HH93AZ169;

Y594G1419

used with T874G1071 (HH07AT171).

Q674Q System: HEAT-OFF-COOL; Fan: LOW-MED-HI-ON

Q1004 59 Obsolete

. McQuay special; used with T874A1267. See OEM for

replacement.

Q1012 64 Used with T874A1291. None

Q674R System: OFF-COOL; Fan: LO-HI-CONT

R1003 69 Obsolete

symbols on fan and switches; used with T874V1008

. Carrier part no. HH93AZ190; international

See OEM for replacement.

(HH07AT177).

Q674S System: HEAT-COOL; Fan: None

S1000 70 Obsolete

with T874C1653; used in Y594C1348.

. Fiberglas; Canada; SERVICE LED; used

See OEM for replacement.

Q674W System: OFF-ON; Fan: LO-MED-HI

W1006 240 Obsolete

. Snyder General part no. 044271801. See OEM for

replacement.

Both the thermostat and subbase must be replaced.

Q674 Trade

Y594R1797

Y594R1797 Wiring differences (old=new):

C/X=X.

Y594R1797 Wiring differences (old=new):

C/X=X, W3=W2.

Y594G1674 Replacement has auto

changeover.

Y594J1019 Replacement has auto

changeover.

Y594R1797

Wiring differences (old=new): C=X; jumper Y1-W1; replacement has OFF-EM HTHEAT-AUTO-COOL system switching.

60-2485—8 86

Page 87

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 10. Y594 Cross Reference.

Model

Number

Fig.

No. Description

Trade Mo del

Replacement

Y594A

A1001 46 Obsolete

T874A1077, Q674B1075.

A1019 82 Obsolete

T874A1077, Q674E1056.

A1035 44 Obsolete

T874A1085, Q674B1018.

A1043 46 Obsolete

T874A1085, Q674B1075.

A1050 55, 66 Obsolete

T874A1085, Q674D1008.

A1068 82 Obsolete

T874A1119, Q674E1007.

. Amana part no. D68535-11; contains

. Amana part no. P68535-12; contains

. Trane part no. 268-0187-1; contains

. Trane part no. 268-0201-5; contains

. Trane part no. 268-0201-3; contains

. Sears part no. 42-9144; contains

T874A1036/ Q674B1075

T874A1036/ Q674E1049

T874A1036/ Q674B1018

T874A1036/ Q674B1075

T874A1036/ Q674D1040

T874A1036/ Q674E1049

A1126 64 Contains T874A1291, Q674Q1012. None

A1159 91 Obsolete

. Contains T874A1440, Q674G1005. T874A1150/

Q674G1070

A1167 184 California Economizer; Premier White® color;

contains T874A1580 and Q674G1161.

A1175 55 Obsolete

. York logo; part no. 2TH04703224;

contains T874A1622, Q674D1180.

A1191 46 Obsolete

. Amana logo: part no. P6853524R;

contains T874A1002, Q674B1075.

T874A1036/ Q674G1070

T874A1010/ Q674D1040

T874A1036/ Q674B1075

Y594B

B1026 44 Trane part no. BAYSTAT012; contains T874B1035,

Q674B1018.

B1034 46 Obsolete

. Trane part no. 163-552-1; contains

T874B1035, Q674B1075.

B1042 88 Obsolete

. Goodman part no. CHTS36-60; contains

T874B1100, Q674E1338.

T874B1019/ Q674B1018

T874B1019/ Q674B1075

T874B1019/ Q674E1049

Y594C

C1009 82 Obsolete

. Amana part no. D68535-9; contains

T874C1059, Q674E1056.

C1017 142 Obsolete. Amana part no. D68535-10; contains

T874C1059, Q674F1022.

C1058 46 Obsolete

. Contains T874C1000, Q674B1075. T874C1018/

T874C1018/ Q674E1049

T874C1018/

Q674F1022

Q674B1075

C1082 82 Obsolete

. Trane part no. 166-162-1; contains

T874C1083, Q674E1007.

C1256 45 Obsolete

. Amana part no. D68535-16; contains

T874C1059, Q674B1059.

C1280 45 Obsolete. Williamson; contains T874C1570,

Q674B1000.

C1314 56 Obsolete

. LSI; contains T874C1471, Q674B1257. T874C1018/

T874C1018/ Q674E1049

T874C1018/ Q674B1034

Q674B1018

C1322 121 Obsolete

C1330 142 Obsolete

T874C1059, Q674F1022.

Both the thermostat and subbase must be replaced.

. Contains T874C1638, Q674L1561. Y594C1322

. Amana part no. D68535-21; contains

T874C1018/

Q674F1022

Remarks

Replacement is beige color.

No LEDs on replacement.

Jumper RC-RH.

Jumper RC-RH; no RESET LED on replacement.

87 60-2485—8

Page 88

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 10. Y594 Cross Reference.

Model

Number

Fig.

No. Description

C1348 70 Obsolete. Fiberglas; contains T874C1653,

Trade Mo del

Replacement

T874C1000/

Q674S1000.

C1355 45 Obsolete

. Nordyne “Miller” part no. 9122250;

T874C1018/

contains T874C1695, Q674B1000.

C1363 45 Obsolete

. Nordyne “Intertherm” part no. 911100001;

T874C1018/

contains T874C1703, Q674B1000.

C1371 184 Obsolete

. California Economizer; contains

T874C1018/

T874C1802 and Q674G1005.

C1389 237 Obsolete

. TRADELINE; Premier White® color;

contains T874C1810 and Q674B1547.

C1413 238 Heat Controller “

Energy Night” logo; contains

T874C1844 and Q674F1592.

C1421 249 Obsolete

. TRADELINE; contains T874C1877 and

Q674B1554.

C1439 T874C1869 and Q674C1579. None

Y594D

D1016 44 Obsolete

. Trane part no. 268-0201-2; contains

T874D1082, Q674B1018.

D1024 72 Trane part no. BAYSTAT010; contains T874D1082,

Q674C1009.

D1032 91 Obsolete

. Trane part no. BAYSTAT011; contains

T874D1082, Q674G1021.

D1040 46 Amana part no. P68535-19R; contains T874D1082,

Q674B1075.

D1057 55, 66 Obsolete

. Trane part no. BAYSTAT007; contains

T874D1082, Q674D1008.

D1149 46 Obsolete

. Amana part no. P68535-20C; contains

T874D1322, Q674B1075.

D1156 48 Obsolete

. Trane part no. BAYSTAT013; contains

T874D1082, Q674B1133.

D1180 82 York part no. 025-23321-000; contains T874D1504,

Q674E1007.

D1222 166 Obsolete

. WeatherKing; contains T874D1009,

Q674F1337.

D1248 82 Obsolete

. Reznor part no. 93437; contains

T874D1629, Q674E1007.

D1297 82 Obsolete

. ArcoAire part no. 1506753; contains

T874D1769, Q674E1346.

D1305 82 Obsolete

. Comfortmaker part no. 1505753; contains

T874D1785, Q674E1346.

D1321 45 Obsolete

. Goodman part no. CHT 90-120; contains

T874D1843, Q674B1000.

D1339 82 Obsolete

. Nordyne part no. 5471180; contains

T874D1009, Q674E1007.

Both the thermostat and subbase must be replaced.

Remarks

Wiring differences (old=new):

Q674B1075

Y=Y1; jumper RC-RH and Y1W1; replacement has no SERVICE LED; replacement has fan switching and HEATOFF-COOL system switching.

Q674B1034

Wiring differences (old=new):

Q674B1075

Y=Y1; jumper RC-RH; Y1-W; replacement has no SERVICE LED.

Q674G1070

Y594C1389

Y594R1425 E-W2 jumper required; system:

EM.HT.-Heat-Off-Cool.

Y594D1347 Replacement has auto

changeover; jumper RH-RC.

T874D1165/

Q674B1018

T874D1165/ Q674C1058

T874D1165/ Q674G1070

T874D1165/

Q674B1075

T874D1165/ Q674D1040

T874D1165/

Q674B1075

T874D1165/

Q674B1018

Replacement has no FILTER LED.

T874D1165/

Q674E1049

T874D1165/

Q674F1022

Wiring differences (old=new): R=RH; jumper RC-RH; replacement has no EM.HT. or AUX. HT. LEDs.

T874D1165/

Q674E1049

T874D1165/

Q674E1049

T874D1165/

Q674E1049

T874D1165/

Q674B1034

T874D1165/

Q674E1049

60-2485—8 88

Page 89

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 10. Y594 Cross Reference.

Model

Number

Fig.

No. Description

Trade Mo del

Replacement

D1347 82 TRADELINE® contains T874D1942, Q674E1403. Y594D1347

D1354 82 SUPER TRADELINE® contains T874D2031 (no

Y594D1354

cover), Q674E1049, and TG504A with two keys.

D1370 45 Obsolete

T874D2049 and Q674B1539.

D1388 72 Obsolete

T874D2049 and Q674C1520.

D1396 184 Obsolete

T874D2049 and Q674G1153.

D1404 55, 66 Obsolete

T874D2049 and Q674D1164.

D1412 82 Obsolete

HH07AT209; taupe color; contains T874D2064 and

. Carrier part no. 50QE90022101; contains

. Carrier part no. 50QE90023101; contains

. Carrier part no. 50QE90025101; contains

. Carrier part no. 50QE90024101; contains

. Carrier “Weathermaker” part no.

T874D1165/ Q674B1034

T874D1165/ Q674C1058

T874D1165/ Q674G1070

T874D1165/ Q674D1040

T874D1165/ Q674E1049

Q674E1445.

D1420 82 Obsolete

HH07AT208; taupe color; contains T874D2072 and

. Carrier “Zone Perfect” part no.

T874D1165/ Q674E1049

Q674E1445.

D1438 55, 66 Obsolete

. Contains T874D2098 and Q674D1008. T874D1165/

Q674D1040

D1446 55, 66 Obsolete

. Contains T874D2106 and Q674D1008. T874D1165/

Q674D1040

D1453 208 Obsolete

contains T874D2163 and Q674D1172.

D1461 45 Obsolete

contains T874D2171 and Q674B1562.

. Amana logo; part no. P1217501F;

. Amana logo; part no. P1217701F;

T874D1165/ Q674D1040

T874D1942/ Q674B1034

Y594E

E1015 72 Obsolete

T874E1040, Q674C1009.

. Trane part no. BAYSTAT015; contains

T874B1019/ Q674C1058

Y594F

F1022 44 Obsolete

. Contains T874F1031 and 40003440-001

T874F1015

wallplate with installed diode.

F1048 72 Obsolete

T874F1130, Q674C1009.

F1063 91 Obsolete

T874F1130, Q674G1005.

. Reznor part no. 93436; contains

. Reznor part no. 93435; contains

T874F1015/ Q674C1058

T874F1015/ Q674G1070

Y594G

G1013 160 Obsolete. York part no. 2TH11702424; contains

Y594G1567

T874G1170, Q674J1027.

G1138 160 Obsolete

. York part no. 025-22286; contains

Y594G1567

T874G1196, Q674J1027.

G1153 154 Obsolete

. Crispaire part no. HP10-51; contains

Y594G1252 Wiring differences (old=new):

T874G1089, Q674F1204.

G1161 162 Contains T874G1204, Q674J1043. Y594G1161

G1195 155 Obsolete

. Heil Quaker part no. HQ521387HW;

Y594G1252

contains T874G1246, Q674F1212.

G1229 160 Obsolete

. York part no. 6TH11702424; contains

Y594G1567

T874G1428, Q674J1027.

G1245 155 Obsolete

. BDP part no. HH641502; contains

Y594G1252

T874G1451, Q674F1212.

G1252 155 TRADELINE; contains T874G1246, Q674F1212. Y594G1252

Both the thermostat and subbase must be replaced.

Remarks

Replacement has °F scaleplate.

Replacement is beige color.

Replacement has 2 setpoint levers.

Replacement has °F scaleplate and 2 setpoint levers.

A=L.

89 60-2485—8

Page 90

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 10. Y594 Cross Reference.

Model

Number

Fig.

No. Description

G1294 79 Obsolete. LSI; contains T874G1378, Q674C1124. See OEM for

Trade Mo del

Replacement

H2 is night setback.

Remarks

replacement.

G1328 194 Obsolete

T874G1543, Q674F1345.

G1344 194 Obsolete

contains T874G1469, Q674F1345.

G1351 160 Obsolete

. Addison part no. 8403-197; contains

. Heat Controller part no. 7601-110B;

. Luxaire part no. 026-00068-000; contains

Y594G1252 Wiring differences (old=new):

Y1=O, X=L, C=X.

Y594G1252 Wiring differences (old=new):

Y1=O, X=L, C=X; W1=Y.

Y594G1567

T874G1568, Q674J1126.

G1369 155 Obsolete

G1377 169 Obsolete. Coleman part no. 3600-373; contains

. Contains T874G1246, Q674F1212. Y594G1252

Y594G1633

T874G1576, Q674F1402.

G1385 155 Obsolete

. ArcoAire; contains T874G1592,

Y594G1252

Q674F1212.

G1393 170 Obsolete

. Contains T874R1393, Q674L1454. Y594G1393

G1419 227 TRADELINE; contains T874G1642, Q674F1444. Y594G1419

G1427 177 Obsolete

T874G1659, Q674C1330.

G1443 174 Obsolete

. Mammoth part no. 73034101; contains

. American Standard (Trane) part no.

See OEM for replacement.

Y594G1161

H2 is night setback.

ASYSTAT650; contains T874G1675, Q674J1142.

G1476 227 TRADELINE; same as Y594G1419 except Premier

Y594G1476

White® color; contains T874G1741, Q674F1477.

G1492 211 Trol-A-Temp; contains T874G1758, Q674F1485. None See Trol-A-Temp for

replacement.

G1500 216 Obsolete

T874G1774, Q674J1175.

G1518 216 Obsolete

T874G1782, Q674J1175.

. Comfortmaker part no. 1505756; contains

. ArcoAire part no. 1506756; contains

See OEM for replacement.

G1526 167 TRADELINE; contains T874G1626, Q674F1436. None

G1534 227 TRADELINE; °C; white; Australia; contains

None

T874G1824, Q674F1477.

G1542 231 Obsolete

. Intertherm part no. 9129290; contains

Y594G1252 Cooling changeover only.

T874G1832, Q674F1519.

G1559 231 Obsolete

. Miller part no. 9129310; contains

Y594G1252 Cooling changeover only.

T874G1840, Q674F1519.

G1567 160 TRADELINE; contains T874G1865, Q674J1209. Y594G1567

G1575 160 Obsolete. TRADELINE; same as Y594G1567

Y594G1567 Replacement is beige. except Premier White® color; contains T874G1873, Q674J1225; direct replacement for York 2TH11702424 (Y594G1013 contains T874G1170/ Q674J1027) and 6TH11702424 (Y594G1229 contains T874G1428/Q674J1027).

G1583 229 Obsolete

T874G1857, Q674F1535.

G1591 243 Obsolete

. Lennox Canada part no. 97E78; contains

. Amana part no. 10636701; contains

Y594G1161 Wiring differences (old=new):

E=X2, C=B, L=F.

Y594G1633 T874G1899 and Q674F1550.

G1609 155 Obsolete

. Econar; contains T874G1915 and

Y594G1252 Q674F1212.

Both the thermostat and subbase must be replaced.

60-2485—8 90

Page 91

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 10. Y594 Cross Reference.

Model

Number

Fig.

No. Description

G1617 73 Obsolete. Carrier part no. 50QE90020101; contains

T874G1949 and Q674C1504.

G1625 160 York Canada part no. 2TH11702524; contains

T874G1964 and Q674J1266.

G1633 169 TRADELINE; contains T874G1972 and

Q674F1584; direct replacement for Y594G1377 (T874G1576/Q674F1402) Evcon/Coleman part no. 3600-373.

G1641 169 Obsolete. Amana part no. 10636703; contains

T874G1980 and Q674F1600.

G1658 155 Obsolete

. Tempstar “Inter-City Products” part no.

1149910; contains T874G1998 and Q674F1212.

G1666 103 Obsolete

. TRADELINE; manual changeover; contains T874G2004 and Q674L1892; direct replacement for Y507J1011 (T874G1055/ Q674L1041) Carrier part no. 99TZ90041106 (HH07AT171/HH93AZ1750).

G1674 161 TRADELINE; automatic changeover; contains

T874G2004 and Q674J1274; direct replacement Y507J1003 (T874G1055/Q674J1035) Carrier part no. 99TZ90040106 (HH07AT171/HH93AZ173).

G1716 155 WaterFurnace logo; part no. TA21H03; contains

T874G2046 and Q674F1667.

Y594H

H1004 79 Obsolete

. LSI part no. 73033901; contains T874H1039 and Q674C1124.

H1012 164 Contains T874H1062 and Q674C1249; replaces

T874H1005/Q674C1041.

H1020 177 Obsolete

. Mammoth part no. 71117101; contains T874H1096 and Q674C1330.

H1038 74 Obsolete

. Carrier part no. 50QE90019101; contains T874H1161 and Q674C1496.

H1046 172 Obsolete

. Carrier part no. 50QE90026101; contains T874H1153 and Q674B1406.

H1053 173 Obsolete. Carrier part no. 50QE90027101; contains

T874H1153 and Q674C1322.

Y594J

J1001 241 Obsolete. TRADELINE; manual changeover;

contains T874J1069 and Q674L1900; direct replacement for T874J1002 or T874A1028 used with Q674L1074 or Q674L1637 (HH07AT175 or HH07AT165 used with HH93AZ186 or HH93AZ195).

Both the thermostat and subbase must be replaced.

Trade Mo del

Replacement

Y594H1012

Wiring differences (old=new):

Remarks

Y1=O, Y2=Y, L=R, R=none; R-L jumper required; no night setback.

T8600D2028

(programmable)

Wiring differences (old=new): Y1=O, Y2=Y, L=R; W-Y jumper required; night setback.

Y594G1567

Replacement has °F scaleplate.

Y594G1633

Y594G1633 Wiring differences (old=new):

W3=W2.

Y594G1252

Y594G1674 Replacement has auto

changeover.

Y594G1674

Y594G1716

T8600D2028 H2 is night setback.

Y594H1012

Y594H1012 Wiring differences (old=new):

R1=R, R2=L; use jumper provided.

Y594H1012

Wiring differences (old=new): X1=O, Y2=Y; L-R jumper required.

T874A1130/

Q674B1075

Wiring differences (old=new):

Y=Y1; W1-Y1 jumper required; replacement has no LEDs.

Y594H1012

Wiring differences (old=new): Z=X.

(Recontrol)

T8511G1021

91 60-2485—8

Page 92

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 10. Y594 Cross Reference.

Model

Number

Fig.

No. Description

J1019 244 Obsolete. TRADELINE; automatic changeover;

contains T874J1069 and Q674J1282; direct

Trade Mo del

Replacement

(Recontrol)

T8511G1021 replacement for T874J1002 or T874J1028 used with Q674J1068 or Q674J1159 (HH07AT175 or HH07AT165 used with HH93AZ183 or HH93AZ196).

Y594N

N1007 178 Obsolete

T874N1008 and Q674F1196.

N1015 179 Obsolete

N1023 178 Obsolete

T874N1057 and Q674F1220.

N1031 178 Obsolete

contains T874N1065 and Q674F1220.

. Williamson part no. 75-189; contains

. Contains T874N1040 and Q674F1261.

. Intertherm part no. 9111882; contains

. Nordyne “Miller” part no. 9122240;

T874N1016/

Q674F1196

Y594G1419

T874N1016/

Q674F1220

T874N1016/

Q674F1220

Y594P

P1005 97 Obsolete

. Carrier part no. 50QE90021101; contains

T8600D2028 Wiring differences (old=new): T874P1055 and Q674C1512.

Y594R

R1011 120 Obsolete

. York part no. 2TH11702224; contains

Y594R1664

T874R1046 and Q674L1272.

R1029 47 Obsolete

. Bryant; contains T874R1004 and

Y594R1243 Wiring differences (old=new):

Q674B1042.

R1037 122 Obsolete

. Fedders part no. 88-58-00540-001;

Y594R1615 Wiring differences (old=new):

contains T874R1269 and Q674L1066.

R1102 120 Obsolete

. York part no. 025-22285-000; contains

Y594R1664

T874R1145 and Q674L1272.

R1110 108 Obsolete

. Heil Quaker part no. HQ712004HW;

Y594R1292

contains T874R1137 and Q674L1132.

R1128 116 Obsolete

. Crispaire part no. HP9-51; contains

Y594R1243 Wiring differences (old=new):

T874 R1111 and Q674L1215.

R1136 109 Obsolete

R1151 120 Obsolete

. Contains T874R1053 and Q674L1140. Y594R1763

. York part no. 2TH11702324; contains

Y594R1672

T874R1251, Q674L1272 and C815A1039.

R1185 201 Obsolete

. Intertherm part no. 9111871; contains

Y594R1672 Wiring differences (old=new):

T874R1202 and Q674L1264.

R1193 120 Obsolete

. York part no. 6TH11702224; contains

Y594R1664

T874R1327 and Q674L1272.

R1201 106 Obsolete

. BDP part no. HH641501; contains

Y594R1243

T874R1335 and Q674L1405.

R1219 133 Obsolete

. Fedders part no. 88-58-00560-001;

Y594R1425 Wiring differences (old=new):

contains T874R1343 and Q674L1413.

R1235 125 Obsolete. Coleman part no. 3600-368; contains

Y594R1797

T874R1368 and Q674L1421.

R1243 115 TRADELINE; contains T874R1152 and Q674L1207. Y594R1243

R1250 128 Obsolete

. Williamson part no. 75-191; contains

Y594R1425 Wiring differences (old=new):

T874R1392 and Q674L1447.

R1284 136 Obsolete

. Trane part no. BAYSTAT339; contains

Y594R1763

T874R1426 and Q674L1496.

Both the thermostat and subbase must be replaced.

Wiring differences (old=new):

Remarks

L=X2, Y=Y1.

Y=Y1, W=O; Y1-W1 jumper required.

W1=W2.

K=E, C=X, W1=B, Z=L.

A=L.

W2=W, X=B, Z=no connection, K=X, W1=H.

K=E, C=X, Z=L; remove factory installed jumper.

A=L.

60-2485—8 92

Page 93

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 10. Y594 Cross Reference.

Model

Number

Fig.

No. Description

R1292 108 Contains T874R1467 and Q674L1512; replaces

Trade Mo del

Replacement

Y594R1292

Remarks

Y594R1110 (T874R1137/Q674L1132).

R1300 123 Contains T874R1475 and Q674L1520. Y594R1300

R1318 130 Obsolete

T874R1483, Q674L1538 and C815A1005.

R1326 137 Obsolete

. Comfortmaker part no. 1505721; contains

. SUPER TRADELINE; contains

Y594R1763 Wiring differences (old=new):

W1=W, E=X2, X=F, C=B.

Y594R1615

T874R1491 and Q674L1553.

R1334 47 Obsolete

Q674B1042.

R1342 130 Obsolete

T874R1517, Q674L1538 and C815A1005.

R1359 113 Obsolete

T874R1525 and Q674L1181.

R1375 130 Obsolete

C815A1005.

R1383 132 Obsolete

T874R1574 and Q674L1538.

R1391 132 Obsolete

T874R1582 and Q674L1538.

R1409 119 Obsolete

T874R1608 and Q674L1264.

. Slant Fin; contains T874R1509 and

. ArcoAire part no. 1506721; contains

. ArcoAire part no. A02074; contains

. Contains T874R1566, Q674L1538 and

. Comfortmaker part no. 1505739; contains

. ArcoAire part no. 1506739; contains

. Intertherm part no. 6244630; contains

Y594R1243 Wiring differences (old=new):

W1=W2.

Y594R1763 Wiring differences (old=new):

W1=W, E=X2, X=F, C=B.

Y594R1243 Wiring differences (old=new):

X1=X.

Y594R1763 Wiring differences (old=new):

W1=W, E=X2, X=F, C=B.

Y594R1243 Wiring differences (old=new):

W=W2, C=X, X=L.

Y594R1243 Wiring differences (old=new):

W=W2, C=X, X=L.

Y594R1763 Wiring differences (old=new):

W2=W, X=B, Z=F, K=X2, W1=O.

R1417 113 Obsolete. Comfortmaker part no. 1505-735;

contains T874R1301 and Q674L1181.

R1425 168 SUPER TRADELINE; contains T874R1616 and

Y594R1243 Wiring differences (old=new):

X1=X.

Y594R1425

Q674L1587.

R1433 200 Obsolete

T874R1624 and Q674L1595.

. Miller part no. 9115900; contains

Y594R1243 Wiring differences (old=new):

W2=W, X=B, Z=F, K=X2, W1=O.

R1441 136 Obsolete

. American Standard (Trane) part no.

Y594R1763 ASYSTAT651; contains T874R1657 and Q674L1611.

R1466 108 Heil Quaker part no. 1060321; model no.

Y594R1292 HAXB004TW01; contains T874R1673 and Q674L1132.

R1482 119 Obsolete

contains T874R1699 and Q674L1264.

. Nordyne “Miller” part no. 9122230;

Y594R1763 Wiring differences (old=new):

W2=W, X=B, Z=F, K=X2, W1=O.

R1490 209 Trol-A-Temp; contains T874R1707 and Q674L1678. None See Trol-A-Temp for

replacement.

R1508 209 Trol-A-Temp; contains T874R1715 and Q674L1686. None See Trol-A-Temp for

replacement.

R1516 132 Obsolete

contains T874R1723, Q674L1702 and C815A1005.

R1524 108 Obsolete

. Snyder General part no. 654958B07;

. Inter-City Products part no.

Y594R1763 Wiring differences (old=new):

W1=W, C=B, X=X2.

Y594R1292 HQ1147925HW; contains T874R1731 and Q674L1132.

R1532 108 Heil Quaker part no. 1060322; model no.

Y594R1292 TAXB004TW01; contains T874R1749 and Q674L1132.

R1607 108 Obsolete

. Keeprite THPC; contains T874R1814 and

Y594R1292 Q674L1132.

Both the thermostat and subbase must be replaced.

93 60-2485—8

Page 94

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 10. Y594 Cross Reference.

Model

Number

Fig.

No. Description

R1615 230 TRADELINE; contains T874R1822 and

Q674L1710; replaces Y594R1326 (T874R1491/ Q674L1553).

R1623 134 Obsolete

. Rheem Universal Parts part no. 41-

20796-46; contains T874R1558 and Q674L1504.

R1631 134 Rheem part no. 41-20796-29; contains T874R1442

and Q674L1504.

R1649 134 Ruud part no. 41-20796-33; contains T874R1434

and Q674L1504.

R1656 134 Obsolete

. WeatherKing part no. 41-20796-64;

contains T874R1830 and Q674L1504.

R1664 120 TRADELINE; contains T874R1871 and

Q674L1736; direct replacement for York 2TH11702224 (Y594R1011 contains T874R1046/ Q674L1272).

R1672 120 TRADELINE; contains T874R1889, Q674L1736

and C815A1054; direct replacement for York 2TH11702324 (Y594R1151 contains T874R1251/ Q674L1272/C815A1039) and 6TH11702224 (Y594R1193 contains T874R1327/Q674L1272).

R1680 230 TRADELINE; same as Y594R1615 except Premier

White® color; contains T874R1897 and Q674L1751; direct replacement for Y594R1326 (T874R1491/Q674L1553).

R1698 120 Obsolete

. TRADELINE; Premier White® color;

contains T874R1905, Q674L1777 and C815A1054.

R1706 120 Obsolete

. TRADELINE; same as Y594R1664 except Premier White® color; contains T874R1913 and Q674L1777; direct replacement for Y594R1011 (T874R1046/Q674L1272) York part no. 2TH11702224.

R1714 228 Obsolete

. Lennox part no. 97E79; Canada; Premier White® color; contains T874R1855 and Q674L1728.

R1722 115 Obsolete

. Econar; contains T874R1921 and Q674L1207.

R1748 197 American Standard (Trane) part no. ASYSTAT651A;

contains T874R1939 and Q674L1801.

R1755 168 Obsolete. Inter-City Products part no.

HQ1149376HW; contains T874R1947 and Q674L1819.

R1763 197 TRADELINE: contains T874R1954 and

Q674L1827; direct replacement for Y594R1136 (T874R1053/Q674L1140), Y594R1748 (T874R1939/Q674L1801) Trane part no. ASYSTAT651A, Y594R1441 (T874R1657/ Q674L1611) Trane part no. ASYSTAT651.

R1771 115 Obsolete

. Consolidated Industries part no. 9036100; contains T874R1962 and Q674L1843.

R1789 120 York Canada part no. 2TH11701524; contains

T874R1970 and Q674L1850.

Both the thermostat and subbase must be replaced.

Trade Mo del

Replacement

Remarks

Y594R1615

Y594R1300

Y594R1664

Y594R1672

Y594R1680

Y594R1672 Replacement is beige.

Y594R1664 Replacement is beige.

Y594R1763 Wiring differences (old=new):

Y1=Y, L=F, W1=W, E=W2, C=B.

Y594R1243

Y594R1763

Y594R1425

Y594R1763

Y594R1680

Y594R1672

Includes CHECK LED.

Replacement has °F scaleplate.

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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

Table 10. Y594 Cross Reference.

Model

Number

Fig.

No. Description

R1797 125 TRADELINE; contains T874R1988 and

Q674L1868; direct replacement for Y594R1235 (T874R1368/Q674L1421) Evcon/Coleman part no. 3600-368).

R1805 245 Obsolete. Amana part no. 10636702; contains

T874R2002 and Q674L1876.

R1813 245 Obsolete

. Amana part no. 10636704; contains

T874R2010 and Q674L1884.

R1821 125 Obsolete

. York logo; part no. 2TH11703424A;

contains T874R2028 and Q674L1918.

R1839 134 Rudd logo; part no. 41-20796-48; contains

T874R2036 and Q674L1504.

R1854 123 Obsolete

. Rheem logo; part no. 41-20796-47;

contains T874R1996 and Q674L1504.

Y594W

W1014 54 Contains T874W1015, Q674B1216 and

C815A1005.

W1022 140 Obsolete

. Rheem part no. 41-20797-19; contains

T874W1031, Q674L1546 and C815A1005.

W1030 68 Obsolete

. Inter-City Products part no. 1072350; contains T874W1072, Q674L1835 and C815A1005 Outdoor Thermistor.

W1055 247 Obsolete

. Addison logo; part no. 843-277; contains T874W1106, Q674L1934 and C815A1005.

Y594Y

Y1004 210 Obsolete. Mammoth part no. 71117301; contains

T874Y1005 and Q674E1353.

Y1012 248 Obsolete

. WaterFurnace logo; part no. TA21H03; contains T874Y1013 and Q674F1675.

Both the thermostat and subbase must be replaced.

Trade Mo del

Replacement

Y594R1797

Remarks

Y594R1797 Wiring differences (old=new):

C/X=X.

Y594R1797 Wiring differences (old=new):

C/X=X, W3=W2.

Y594R1797

See OEM for replacement.

Y594R1300

Y594W1014

T8611M2025.

T8611M2025

Includes night setback.

(programmable)

T8611M2025

See OEM for replacement.

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WIRING DIAGRAMS

FALL

H1 ANTICIPATOR

FALL

RISE

THERMOSTAT

H2 ANTICIPATOR

C1 ANTICIPATOR

C2 ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

JUMPER RH, RC FOR SINGLE TRANSFORMER.

SUBBASE SYSTEM COMPONENTS

HEAT RELAY 1

FAN SWITCH

AUTO

SYSTEM SWITCH

HEAT

OFF

COOL

HEAT RELAY 2

HEAT CHANGEOVER VALVE

COOL CHANGEOVER

VALVE

FAN RELAY

COMPRESSOR CONTACTOR 2

COMPRESSOR CONTACTOR 1

M2903

L1 (HO

L2 L1

(HO

Fig. 44. Schematic and hookup of T874A,B,C,D,E,F with Q674B. Used in standard applications.

NOTE:

Model Heating Cooling No. Bulbs Bulbs

T874A H1 C1 T874B H1 C1,C2 T874C H1,H2 C1 T874D H1,H2 C1,C2 T874E C1,C2 T874D H1,H2

SUBBASE SYSTEM COMPONENTS

FAN SWITCH

AUTO

SYSTEM SWITCH

HEAT

OFF

COOL

OPTIONAL LED ON SOME MODELS.

HEAT RELAY 1

HEAT RELAY 2

HEAT CHANGEOVER VALVE

COOL CHANGEOVER VALVE

FAN RELAY

COMPRESSOR CONTACTOR 2

COMPRESSOR CONTACTOR 1

L1 (HO

L2 L1

(HO

M933C

FALL

H1 ANTICIPATOR

FALL

RISE

THERMOSTAT

H2 ANTICIPATOR

C1 ANTICIPATOR

C2 ANTICIPATOR

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

JUMPER RH, RC FOR SINGLE TRANSFORMER.

Fig. 45. Schematic and hookup of T874C,D with Q674B. Used in standard applications.

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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

PROTECTION AS REQUIRED.

)

CONTACTOR

FALL

H1 ANTICIPATOR

FALL

RISE

THERMOSTAT

H2 ANTICIPATOR

C1 ANTICIPATOR

C2 ANTICIPATOR

SUBBASE

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

FAN SWITCH

AUTO

SYSTEM SWITCH

HEAT

OFF

COOL

SYSTEM COMPONENTS

HEAT RELAY 1

HEAT RELAY 2

HEAT CHANGEOVER VALVE

COOL CHANGEOVER VALVE

FAN RELAY

COMPRESSOR CONTACTOR 2

COMPRESSOR CONTACTOR 1

Fig. 46. Schematic and hookup of T874A,B,D with Q674B. Used in standard applications.

M2904

L1 (HOT

SUBBASE SYSTEM COMPONENTS

COOL CHANGEOVER

AUTO

HEAT OFF

COOL

VALVE

FAN RELAY

AUX. HT. RELAY

COMPRESSOR

L1 (HO

M2906

FALL

THERMOSTAT

H1/C1 ANTICIPATOR

FALL

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

FAN SWITCH

SYSTEM SWITCH

Fig. 47. Schematic and hookup of T874R with Q674B. Used in heat pump applications.

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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

)

THERMOSTAT

FALL

H1 ANTICIPATOR

FALL

RISE

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

CLOGGED FILTER, SERVICE SWITCH.

H2 ANTICIPATOR

C1 ANTICIPATOR

C2 ANTICIPATOR

FAN SWITCH

AUTO

SYSTEM SWITCH

HEAT

OFF

COOL

SUBBASE

FILTER LED (RED)

SYSTEM COMPONENTS

HEAT RELAY 1

FAN RELAY

EXTERNAL FAN SWITCH

HEAT RELAY 2

HEAT CHANGEOVER VALVE

COOL CHANGEOVER VALVE

COMPRESSOR CONTACTOR 1

COMPRESSOR CONTACTOR 2

L1 (HOT

M2905

(HOT

Fig. 48. Schematic and hookup of T874D with Q674B. Used in standard applications.

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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

)

THERMOSTAT SUBBASE

H1 ANTICIPATOR

FALL

H2 ANTICIPATOR

FALL

C1 ANTICIPATOR

RISE

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

FAN SWITCH

AUTO

SYSTEM SWITCH

HEAT

OFF

COOL

HEAT LED (RED)

LO SPEED LED (GREEN)

HI SPEED LED (GREEN

COOL LED (YELLOW)

SYSTEM COMPONENTS

HEAT RELAY 1

BLOWER RELAY

HEAT RELAY 2

COMPRESSOR CONTACTOR

HSII CONTROL PANEL

L1 (HOT

M594

Fig. 49. Schematic and hookup of T874C with Q674B. Used in standard applications.

THERMOSTAT

H1 ANTICIPATOR

FALL

RISE

H2 ANTICIPATOR

C1 ANTICIPATOR

RISE

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

SUBBASE SYSTEM COMPONENTS

COOL CHANGEOVER VALVE

FAN SWITCH

AUTO

SYSTEM SWITCH

HEAT

OFF

COOL

AUX. HT. RELAY

COMPRESSOR CONTRACTOR

FAN RELAY

L1 (HOT)

M8000

Fig. 50. Schematic and hookup of T874G with Q674B. Used in heat pump applications.

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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES

B, O TERMINALS ON SOME MODELS.

THERMOSTAT SUBBASE

FALL

H1 ANTICIPATOR

FALL

H2 ANTICIPATOR

RISE

C1 ANTICIPATOR

RISE

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

FIELD WIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER.

C2 ANTICIPATOR

FAN SWITCH

AUTO

SYSTEM SWITCH

HEAT

OFF

COOL

SYSTEM COMPONENTS

HEAT RELAY 1

FAN RELAY

L1 (HOT)

HEAT CHANGEOVER VALVE

L1 (HOT)

COOL CHANGEOVER VALVE

COMPRESSOR CONTACTOR 1

COMPRESSOR CONTACTOR 2

HEAT RELAY 2

M594

Fig. 51. Schematic and hookup of T874D with Q674B. Used in standard applications.

THERMOSTAT

H1 ANTICIPATOR

FALL

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

OPTIONAL FIELD WIRE JUMPER. W3 AND F TO BE JUMPERED EXCEPT FOR TWO STAGE GAS APPLICATION.

FIELD WIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER.

RISE

H2 ANTICIPATOR

C1 ANTICIPATOR

SUBBASE

FAN SWITCH

AUTO

SYSTEM SWITCH

HEAT

OFF

COOL

HEAT RELAY 1

SYSTEM COMPONENTS

HEAT RELAY 2

COMPRESSOR CONTACTOR

FAN RELAY

L1 (HOT)

M5999

Fig. 52. Schematic and hookup of T874C with Q674B. Used in standard applications.

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