Honeywell T841A, T841A1498, T841A1423, T841A1464, T841A1308 User Manual

T841A Heating-Cooling
Heat Pump Thermostat

APPLICATION

The T841A Heating-Cooling TRADELINE® Thermostat
provides 24 Vac control of two-stage heating and one­stage cooling in heat pump systems, using manual
changeover. This thermostat provides SYSTEM switch
selections of EM. HEAT-HEAT-OFF-COOL and FAN
switch selections of AUTO-ON. See Fig. 1. See Table 1 for
T841A TRADELINE® specifications.

Table 1. T841A TRADELINE® Specifications.

OS Number

T841A1308 EM. HEATa,

T841A1316 G, R, E, L, X

T841A1423bEM. HEAT,

T841A1464
T841A1498 EM. HEAT Stage 2 fixed,

T841A1506

a

EM. HEAT LED also indicates compressor malfunction.

b

Premier White® color.

c

Sold only in Australia: degrees C.

d

CHECK LED indicates compressor malfunction.

LED

Indication Changeover

AUX. HEAT

AUX. HEAT,

d

CHECK

b,c

b

FRONT OF DEVICE

Manual Cool
or Heat

Heat

Anticipation

Stage 2 fixed,
0 to 1.5A

Stage 2
adjustable, 0.1
to 1.2A

0 to 1.5A

80

80

70

70
60

60

50

50

CHECK

EM. HEAT HEAT OFF COOL

SYSTEM SWITCH

FAN

AUTO ON

EM. HEAT AUX. HEAT

FAN SWITCH

Fig. 1. External view of T841A.

Test holes are provided on the front of the thermostat to
accommodate test meter probes without removing the
thermostat from the wall. Remove the cover of the
thermostat to expose the test holes, which are labeled to
correspond with the terminals on the back of the
thermostat.

Terminal

Designations Remarks

G, R, W2, E,
L, B, X, Y, O

W2, B, W1,
Y1, O
W3, G, R, W2,
E, L, B, X, Y,
O

G, R, W, H, B,
X, O, Y

COVER

THERMOMETER

SET POINT
SCALE

LED (UP
TO THREE)

INSTALLATION INSTRUCTIONS

System

Switch

EM. HEAT,
HEAT, OFF,
COOL

2

WIRING TERMINAL
(UP TO 12)

MOUNTING
HOLES (4)

Use when E
and W2 are
jumpered.
Does not
replace
T841A1068.
Not for systems
with E to W
jumper

Exact
replacement for
York model no.
2TH11703324

BACK OF DEVICE

Auto Fan

in EM.

HEAT

No

Yes

M2960A

®U.S. Registered Trademark
Copyright © 1997 Honeywell Inc. • • All Rights Reserved

X-XX UL

69-0452-8

T841A HEATING-COOLING HEAT PUMP THERMOSTAT

OPERATION

The stages of heat
drops.

Make

heat or cool.

There is about 1°F (0.6°C) between stages so the second
stage (auxiliary heat) makes only when the first stage
cannot handle the load. This 1°F is the

tial

.

The LED indicators on certain thermostat models light up
when something specific happens within the system.
When the green or amber LED lights, the auxiliary heat
(second stage heat) is operating because the weather is
so cold, the heat pump alone cannot handle the load.
When the red EM. HEAT LED lights, the emergency heat
is operating (usually electric strip heaters), because the
homeowner has physically switched to the EM. HEAT
position. See heating/cooling manufacturer instructions for
specific meaning.

make

refers to the mercury switch initiating a call for

sequentially as the temperature

interstage differen-

RECYCLING NOTICE

This control contains mercury in a sealed tube. Do

not

place the 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
your old control in the trash.

Contact your local waste management authority for
instructions regarding recycling and the proper
disposal of this control, or any 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 technician.

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

not

place

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 thermo­stat base.

3. Do not overtighten the thermostat captive
mounting screws, because damage to the
threads can result.

4. Do not short across coil terminals on the relay.
This can burn out the thermostat heat
anticipator.

5. Never install more than one wire per terminal
unless a factory-supplied jumper with spade
terminal is used.

Location

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

Do not mount 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, appliances or fireplaces.
— concealed pipes and chimneys.
— unheated (uncooled) areas such as an outside wall

behind the thermostat.

This thermostat is a precision instrument and was carefully
adjusted at the factory.

Handle it carefully.

Mounting and Wiring

CAUTION

Disconnect power supply before beginning
installation. Can cause electrical shock or

equipment damage.

The T841A can be mounted directly to a wall or
horizontal outlet box. Choose the method that best fits
your installation.

In replacement applications, check the existing thermostat
wires for cracked or frayed insulation. Replace wires in
poor condition.

All wiring must comply with local codes and ordinances.

69-0452—8

2

T841A HEATING-COOLING HEAT PUMP THERMOSTAT

Grasp the thermostat cover at the top and bottom with one
hand. Pull outward on the bottom edge of the cover until it
snaps free of the thermostat base. Carefully remove and
save the packing material surrounding the mercury
switches.

1. Run the wiring (if necessary) to the location. If the

wiring is plastered into the wall, make a hole next to
the cable and loosen the wires so that they can be
pushed back into the wall later. Thread the wires
through the hole in the packing material saved
above. Connect the wires to the terminals on the
back of the thermostat. See Fig. 2 through 5.

2. Set the second stage adjustable heat anticipator to

match the current draw of the primary heating
control (see Heat Anticipator Setting section).

3. Push the excess wire back through the hole and

plug any opening with packing material to prevent
drafts that may affect thermostat performance.

4. Use screws to loosely secure the thermostat to the

wall or outlet box through the two mounting holes in
the middle of the device.

The sheetmetal screws included with the thermostat are
designed for use in plaster walls that do not need anchors.

IMPORTANT

An incorrectly leveled thermostat causes
inaccurate temperature control.

5. Level the thermostat using a spirit level or plumb

line. Tighten the two mounting screws at the middle
of the device.

6. Install the two screws in the top mounting holes and

tighten.

7. Replace the thermostat cover.

H1

C1

H1 & C1
ANTICIPATOR

FALL

FAN
SWITCH

AUTO

ON

H2 ANTICIPATOR

SYSTEM

H2

FALL

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

1

PROTECTION AS REQUIRED.

WHEN SYSTEM MONITOR IS CONNECTED TO L TERMINAL, EM. HT.

2

LED ALSO INDICATES COMPRESSOR MALFUNCTION.

X TERMINAL MUST BE CONNECTED FOR PROPER OPERATION.

3

Fig. 2. Internal schematic and typical wiring diagram for TRADELINE® T841A1308 with EM. HEAT and AUX. HEAT

LEDs. No fan control in EM. HEAT. Provides heat or cool changeover relay control.

SWITCH

EM. HEAT

HEAT

OFF

COOL

SETTINGS

Heat Anticipator Setting

The second stage heat anticipator is adjustable. Move the
adjustable indicator to match the current draw of the
second stage heating primary control, or the anticipator
setting of the old thermostat. See Fig. 6.

Temperature Setting

Move the setpoint lever to the desired control point on the
temperature scale.

SYSTEM Switch Setting

The SYSTEM switch positions control the system opera­tion as follows:

EM. HEAT: Emergency heat relay is energized. Cooling

system is off. Compressor is de-energized. Fan runs
on call for heat if FAN switch is in the AUTO
position. EM. HEAT LED is on.

HEAT: Heating system is automatically controlled by

the thermostat. Cooling system is off.

OFF: Both the heating and cooling systems are off. If

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

COOL: Cooling system is automatically controlled by

the thermostat. Heating system is off.

FAN Switch Setting

AUTO: Fan operates in response to thermostat in both

heating and cooling.

ON: Fan operates continuously.

L1

1

M1099B

(HOT)
L2

69-0452—8

AUX. HT.
LED (GREEN)

EM. HT.
LED
(RED)

3

ODT 1

RTD 1

EHR 1

RTD 2

ODT 2

RTD 3

LACO

ERH 2

RD

CHANGEOVER
RELAY (HEAT)

COMPRESSOR
CONTACTOR

CHANGEOVER
RELAY (COOL)

RTD 1

EM. HEAT
RELAY

CHP

FAN RELAY

G

R

SYSTEM
MONITOR

W2

E

L

B

2

X

3

Y

O

T841A HEATING-COOLING HEAT PUMP THERMOSTAT

L1
(HOT)

1

CHANGEOVER

CHANGEOVER
RELAY (HEAT)

COMPRESSOR
CONTACTOR

RELAY (COOL)

FAN RELAY

EM. HT.
RELAY

AUX. HT.
RELAY

HEAT RELAY 1

M1103E

O

H1

H2

1

2

3

4

Fig. 3. Internal schematic and typical wiring diagram for SUPER TRADELINE® T841A1316 with AUX. HEAT and

EM. HEAT LEDs. Provides heat or cool changeover relay control and automatic fan in EM. HEAT mode.

FALL

C1

H1 ANTICIPATOR

C1 ANTICIPATOR

FALL

H2 ANTICIPATOR

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

REMOVE W1-Y1 JUMPER WHEN HEAT RELAY 1 IS USED.

WHEN L TERMINAL IS CONNECTED TO SYSTEM MONITOR, EM. HEAT LED ALSO INDICATES COMPRESSOR MALFUNCTION.

X TERMINAL MUST BE CONNECTED FOR PROPER OPERATION.

FAN SWITCH

AUTO

ON

SYSTEM

SWITCH

EM. HT.

HEAT

OFF

COOL

EM. HT.
LED (RED)

AUX. HT.
LED (GREEN)

L

SYSTEM

3

MONITOR

G

R

E

4

X

W2

B

W1

2

JUMPER

Y1

L2

AUTO

SYSTEM
SWITCH

3

EM. HT.

HEAT

COOL

ON
FAN

SWITCH

OFF

EM. HT.
LED (RED)

4

FALL

H1

C1

H1/C1
ANTICIPATOR

H2
ANTICIPATOR

FALL

H2

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND

1

OVERLOAD PROTECTION AS REQUIRED.

2

B TERMINAL MUST BE CONNECTED FOR PROPER OPERATION.

3

AUTO FAN IN EM. HEAT.

Fig. 4. Internal schematic and typical wiring diagram for TRADELINE® T841A1498 and T841A1506

with EM. HEAT LED. Provides cooling changeover relay control.

69-0452—8

G

R

W

H

2

B

X

O

Y

FAN RELAY

HEAT RELAY

"H" RELAY

EM. HT. RELAY

CHANGEOVER
RELAY (COOL)

COMPRESSOR
CONTACTOR

M3171B

L1
(HOT)

L2

1

T841A HEATING-COOLING HEAT PUMP THERMOSTAT

AUX. HT.
LED (GREEN)

EM. HT.
LED (RED)

W3

G

R

W2

E

L

CHECK
LED (RED)

B

X

Y

O

8

EM. HT.

HEAT

OFF

COOL

FAN
SWITCH

AUTO

ON

SYSTEM
SWITCH

2

H1

C1

FALL

H1/C1
ANTICIPATOR

H2

1

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

AUTO FAN IN EM. HEAT.

2

FALL

5

9

3

4

12

11

10

6

LACO

RTD 1

RD

ODT 1

EHR 1

ODT 2

FAN REALY

EM. HT. RELAY

SYSTEM MONITOR

HEAT CHANGE­OVER VALVE

COMPRESSOR
CONTACTOR

COOL CHANGE­OVER VALVE

RDT 2

RTD 3EHR 2

RTD 1

1

L1
(HOT)

CHP

M6059C

L2

Fig. 5. Internal schematic and typical wiring diagram for TRADELINE® T841A1423 and T841A1464 (sold only in

Australia) with AUX. HEAT, EM. HEAT and CHECK LEDs. Provides heat or cool changeover relay control and

automatic fan in EM. HEAT mode.

.10

.12

.15

1.2

.8.6.4

.2

.3

LONGER

EM.HEAT HEAT OFF COOL

MOVE INDICATOR
TO MATCH CURRENT
RATING OF PRIMARY CONTROL

M2962B

Fig. 6. Second stage adjustable heat anticipator indicator.

5

69-0452—8

T841A HEATING-COOLING HEAT PUMP THERMOSTAT

CHECKOUT

Heating

Move the SYSTEM switch on the thermostat to HEAT and
the FAN switch to AUTO. Move the setpoint lever to about
10°F (6°C) above the room temperature. Heating should
start and the fan should run. Move the setpoint lever about
10°F (6°C) below the room temperature. Heating and fan
should shut off.

NOTE: To prevent compressor short cycling, a minimum-

off timer may be included to prevent the com­pressor from starting for up to five minutes from
when the thermostat last turned the compressor
off, or from when the system first received power.

Cooling

CAUTION

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

Move the SYSTEM switch on the thermostat to COOL
and the FAN switch to AUTO. Move the setpoint lever
about 10°F (6°C) below the room temperature. Cooling
and fan should start. Move the setpoint lever about 10°F
(6°C) above the room temperature. Cooling and fan
should shut off.

Fan

Move the SYSTEM switch to OFF, and the FAN switch to
ON. The fan should run continuously. Move the FAN
switch to AUTO. In this position, the fan operates in
response to the thermostat in both heating and cooling.

Automation and Control Solutions

Honeywell International Inc.
1985 Douglas Drive North
Golden Valley, MN 55422

69-0452—8 J.S. Rev. 5-97 www.honeywell.com/yourhome

69-0452—8

Honeywell Limited-Honeywell Limitée
35 Dynamic Drive
Scarborough, Ontario M1V 4Z9

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