T874R Thermostats and Q674L Subbases
Installation Instructions for the Trained Service Technician.
INSTALLATION INSTRUCTIONS
APPLICATION
The T874R Thermostat and Q674L Subbase provide 24 to 30 Vac control of 2-stage heating and 1-stage cool-ing heat pump systems with manual changeover. Q674L Subbase provides EM.HT.-HEAT-OFF-COOL system switching and AUTO-ON fan switching. See Table 1 for specific T874R/Q674L combinations.
Table 1. Thermostat/Subbase Specifications.
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Thermostat/ |
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Thermostat/ |
Subbase |
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Subbase |
Model |
LED |
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See |
Package |
Numbers |
Indication |
Changeover |
Comments |
Fig. |
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Y594R1243 |
T874R1152/ |
AUX.HT., |
Manual Cool |
TRADELINE®; adjustable stage 2 |
6 |
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Q674L1207 |
EM. HT. |
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heat anticipation. Fixed anticipation |
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in stage 1. Auto fan in EM.HT. |
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Y594R1300 |
T874R1475/ |
AUX.HT., |
Manual Heat |
TRADELINE®; fixed heat |
7 |
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Q674L1520 |
EM. HT.a |
or Cool |
anticipation. Auto fan in EM.HT. |
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Y594R1425 |
T874R1616/ |
AUX.HT., |
Manual Heat |
SUPER TRADELINE®; fixed heat |
8 |
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Q674L1587 |
EM. HT., |
or Cool |
anticipation. Factory installed jumper |
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CHECK |
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across W1 and Y1. Auto fan in |
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EM.HT. |
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Y594R1615 |
T874R1822/ |
AUX.HT., |
Manual Heat |
TRADELINE®; fixed heat |
10 |
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Q674L1710 |
EM. HT., |
or Cool |
anticipation. Auto fan in EM.HT. |
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CHECK |
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Y594R1664 |
T874R1871/ |
EM. HT. |
Manual Cool |
TRADELINE®; exact replacement |
9 |
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Q674L1736 |
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for York model no. 2TH11702224. |
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Y594R1672 |
T874R1889/ |
EM. HT. |
Manual Cool |
TRADELINE®; exact replacement |
11 |
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Q674L1736 |
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for York model nos. 2TH11702324 |
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and 6TH11702224. |
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Y594R1698b |
T874R1905/ |
EM. HT. |
Manual Cool |
TRADELINE®; exact replacement |
11 |
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Q674L1777 |
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for York model nos. 2TH11702324 |
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and 6TH11702224. Includes |
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C815A1054 Outdoor Thermistor. |
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Y594R1706b |
T874R1913/ |
EM. HT. |
Manual Cool |
TRADELINE®; exact replacement |
9 |
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Q674L1777 |
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for York model no. 2TH11702224. |
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Y594R1763 |
T874R1954/ |
AUX.HT., |
Manual Cool |
Requires C815A Outdoor Thermister |
5 |
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Q674L1827 |
EM. HT.a |
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for outdoor reset. Fixed stage 1 heat |
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anticipation. No heat anticipation in |
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stage 2 heat. Auto fan in EM.HT. |
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Replaces Y594R1136. |
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Y594R1797 |
T874R1988/ |
AUX.HT., |
Manual Heat |
TRADELINE® |
12 |
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Q674L1868 |
EM.HT. |
or Cool |
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aEM.HT. LED also shows compressor malfunction.
bPremier White® color.
®U.S. Registered |
Trademark |
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69-0392-9 |
Copyright © 1997 |
Honeywell Inc. • |
• All Rights Reserved |
X-XX UL |
T874R THERMOSTATS AND Q674L SUBBASES
OPERATION
On a 2-heat thermostat, the two stages of heat make sequentially as the temperature drops. Make refers to the mercury switch initiating a call for heat or cool.
There is about 1° F (0.6° C) between stages so the second stage makes only when the first stage can not handle the load. The 1° F (0.6° C) is referred to as the interstage differential.
The light emitting diodes (LED) on the subbase light when something specific happens within the system. When an LED lights, refer to this list for the meaning:
EM. HT.: Emergency heat is operating. The compressor has failed, and the heat pump is not operating. LED lights when system switch is placed in the EM.HT. position by the homeowner.
AUX.HT.: Auxiliary heat is operating, which means the weather is so cold that the heat pump cannot handle the load.
CHECK: System needs to be checked. See heating sys-tem instructions for specific meaning.
NOTE: LEDs are not field replaceable or addable.
RECYCLING 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 mer-cury 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.
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 in the instructions and 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
1.Disconnect power supply to prevent electrical shock or equipment damage.
2.To prevent interference with the thermostat linkage, keep wire length to a minimum and run wires as close as possible to the subbase.
3.Push excess wire back into the hole and plug hole to prevent drafts from affecting thermostat operation.
4.Do not overtighten thermostat captive mounting screws because damage to subbase threads can result.
5.Do not short across coil terminals on heating relay or gas valve. This can burn out the thermostat heat anticipator.
6.Never install more than one wire per terminal unless factory-supplied jumper with spade terminals is used.
IMPORTANT
Thermostats are calibrated at the factory using subbase mounted at true level. Inaccurate subbase leveling causes the actual temperature to deviate from the setpoint temperature.
Location
Install the thermostat about 5 ft (1.5m) above the floor in an area with good air circulation at average temperature. Do not install the thermostat where it can be affected by:
—drafts or dead spots behind doors and in corners.
—hot or cold air from ducts.
—radiant heat from sun or appliances.
—concealed pipes and chimneys.
—unheated (uncooled) areas such as an outside wall behind the thermostat.
Mounting The Subbase
The thermostat subbase can be mounted on a vertical outlet box, horizontal outlet box or directly on the wall.
1.If you must mount the subbase on a vertical outlet box, order Honeywell 193121A Adapter Assembly. See Fig. 1. 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.
For a wall installation, hold subbase in position and mark holes for anchors. See Fig. 2. Obtain wall anchors locally. Be careful that the wires do not fall back into the wall opening. Set aside subbase. Drill two 3/16 in. (5 mm) holes and gently tap anchors into the holes until flush with the wall.
69-0392—9 |
2 |
T874R THERMOSTATS AND Q674L SUBBASES
VERTICAL
OUTLET |
1 |
BOX |
COVER
ADAPTER |
PLATE 2 |
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RING 2 |
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MOUNTING |
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SCREWS (2) |
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SUBBASE |
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MOUNTING |
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SCREWS (2) |
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HORIZONTAL |
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OUTLET |
MOUNTING |
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BOX 1 |
SCREWS (2) |
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SUBBASE |
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1 NOT INCLUDED WITH UNIT. |
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2 ACCESSORY PARTS AVAILABLE (193121A). |
M925 |
Fig. 1. Installation of subbase on outlet box.
WALL
WIRES THROUGH
WALL OPENING
WALL |
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ANCHORS |
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MOUNTING |
(2) |
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HOLES |
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MOUNTING |
M926 |
SUBBASE |
SCREWS (2) |
Fig. 2. Installation of subbase on wall.
2.Run wires to the thermostat location.
3.Pull wires through the cover plate (if used) and subbase cable opening. See Fig. 3.
IMPORTANT
Use 18 gauge, color-coded thermostat cable for proper wiring.
4.Secure the cover plate (if used) and subbase with the screws provided. Do not fully tighten the subbase screws.
5.Level the subbase by using a spirit level. Firmly tighten subbase mounting screws. See Fig. 3. The subbase mounting holes provide for minor out-of- level adjustments.
IMPORTANT
An incorrectly leveled subbase causes the temperature control to deviate from setpoint.
Wiring the Subbase
All wiring must comply with local electrical codes and ordinances. Follow equipment manufacturer wiring instructions when available. To wire subbase, proceed as follows:
1.Connect the system wires to the subbase. See Fig. 5-12. A letter code for identification is located near each terminal. The terminal barrier permits straight or conventional wraparound wiring connection. See Fig. 4.
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 the hole with nonflammable insulation to prevent drafts from affecting the thermostat.
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TOP |
WIRING |
THERMOSTAT |
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MOUNTING |
TERMINAL |
CABLE OPENING |
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SPIRIT LEVEL |
HOLES (2) |
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MOUNTING |
POST (2) FOR |
TO SPRING FINGER |
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HOLES (2) |
MOUNTING |
CONTACTS ON THE |
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THERMOSTAT |
THERMOSTAT |
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(UP TO 12) |
M927 |
Fig. 3. Subbase components and leveling procedure.
FOR STRAIGHT |
FOR WRAPAROUND– |
INSERTION– |
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STRIP 5/16 IN. (8 MM) |
STRIP 7/16 IN. (11 MM) |
BARRIER |
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SUBBASE TERMINAL SCREW |
M928 |
Fig. 4. Wiring connections.
3 |
69-0392—9 |
T874R THERMOSTATS AND Q674L SUBBASES
THERMOSTAT |
SUBBASE |
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SYSTEM COMPONENTS |
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1 |
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G |
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FAN RELAY |
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W |
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2 |
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AUX. HT. |
2 |
AUX. HEATER |
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AUTO |
RELAY |
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LED (GREEN) |
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U |
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H1 |
C1 |
ON |
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B |
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FALL |
3 |
FAN |
EM. HT. |
COMPRESSOR |
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MONITOR |
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SWITCH |
LED (RED) |
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F |
1 |
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4 |
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R |
L1 |
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(HOT) |
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L2 |
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H2 |
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FALL |
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SYSTEM |
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SWITCH |
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EM. HT. |
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T |
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6 |
HEAT |
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OUTDOOR |
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X2 |
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THERMISTOR |
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OFF |
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OUTDOOR |
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11 |
COOL |
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THERMOSTAT |
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O |
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COMPRESSOR |
COOL |
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CHANGEOVER |
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RELAY |
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1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND |
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VALVE |
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OVERLOAD PROTECTION AS REQUIRED. |
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Y |
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FIELD REMOVABLE JUMPER. |
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M2970 |
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Fig. 5. Internal schematic and typical wiring diagram for Y594R1763 (T874R1954/Q674L1827). Replaces GE AY28X078, AY28X139; Trane Baystat 139, Baystat 239 and Baystat 240;
and Honeywell Y594R1136 Thermostats.
THERMOSTAT |
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H1/C1 |
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ANTICIPATOR |
FALL |
2 |
H1 |
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C1 |
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3 |
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4 |
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H2 |
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ANTICIPATOR |
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H2 |
6 |
FALL |
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SUBBASE |
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SYSTEM COMPONENTS |
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(HOT) L1 |
L2 |
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1 |
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R |
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ODT 1 |
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RTD 1 |
EHR 1 |
RTD 2 |
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W3 |
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FAN SWITCH |
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ODT 2 |
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AUTO |
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ON |
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EHR 2 |
RTD 3 |
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W2 |
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AUX. HT. |
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RTD 1 |
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LED |
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(GREEN) |
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2 |
X |
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SYSTEM |
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EM. HT. |
SYSTEM |
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LED (RED) |
MONITOR |
RD |
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SWITCH |
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L |
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FAN RELAY |
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EM. HT. |
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G |
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HEAT |
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O |
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EM. HT. |
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COOL CHANGEOVER |
RELAY |
OFF |
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E |
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VALVE |
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COOL |
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LACO |
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CHP |
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Y |
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COMPRESSOR |
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B |
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CONTACTOR |
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1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
M5072A
2 AUXILIARY HEAT LED AVAILABLE ON SOME MODELS.
Fig. 6. Internal schematic and typical wiring diagram for Y594R1243 (T874R1152/Q674L1207).
69-0392—9 |
4 |
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