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