Honeywell t841e, t841d Installation Instructions Manual

Honeywell

T841D,E

Heating-Cooling Thermostats

INSTALLATION INSTRUCTIONS

Installation Instructions for the Trained Service Technician.

APPLICATION

T841 Thermostats provide 24 Vac control of multistage
heating and cooling systems using manual changeover.
The T841D controls 1-stage heat and 2-stage cool and the
T841E controls 2-stage gas heat and 1-stage cool. The
T841D,E, provide HEAT-OFF-COOL system switching
and AUTO-ON fan switching.

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 terminals on back of the thermostat. See
Fig. 1.

Table 1. Thermostat Features.

Order Number LEDs Terminal Designations System Switch Fan Switch

Fig.
T841D CHECK, HI SPD, LO SPD R,G,W,B,L,X,Y1,Y2,O HEAT-OFF-COOL AUTO-ON 2
T841E HI, LOW R,G,W1,B,W2,Y HEAT-OFF-COOL AUTO-ON 3

F R O N T O F D E V IC E B A C K O F D E V IC E

-S YSTEM SWITCH

FAN SWITCH

THERMOMETER

SETPOINT
SCALE

- LED (UP
TO THREE)

MOUNTING
HOLES (4)

WIRING TERM INAL 1
(UP TO 12)

COVER

Fig. 1. External view of T841.

OPERATION

The T841E 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 (auxiliary heat) makes only when the first stage
cannot handle the load. This 1°F is the interstage differen
tial. The T841D stages of COOL-ON make sequentially as
the temperature rises.

The light emitting diodes (LED) indicators light on certain
thermostats when something specific happens within the
system. Refer to the following list when the LED lights:

HI: Stage two of heat is operating.

LOW: Stage one of heat is operating.

CHECK: System needs to be checked. See heating

system instructions for specific meaning.

HI SPD: Stage two of cooling is operating.

LO SPD: Stage one of cooling is operating.

LEDs are not field replaceable.

®U.S. Registered Trademark
Copyright © 1997 Honeywell Inc.

All Rights Reserved

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T841D,E HEATING-COOLING THERMOSTATS

® 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
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.

INSTALLATION

When Installing this Product...

1. Read these instructions carefully. Failure to follow
them could damage the product or cause a hazard
ous 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.

CAUTION

1. Disconnect power supply to prevent electrical
shock or equipment damage.

2. Keep wire length to a minimum and run wires
as close as possible to the thermostat.

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

4. Never install more than one wire per terminal
unless 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 temperature.

Do not mount the thermostat where it may 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 carefully.

Mounting and Wiring

The T841 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 thermo
stat wires for cracked or frayed insulation. Replace any
wires in poor condition. All wiring must comply with local
codes and ordinances.

O Grasp the thermostat cover at the top and bottom

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

e Run 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 they can be pushed
back into the wall later. Thread wires through the
hole in packing material saved in step 1. Connect
the wires to the terminals on the back of the
thermostat. See Fig. 2 or 3.

© Where applicable, set the adjustable heat anticipator

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

Q Push the excess wire back through the hole and

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

0 Loosely secure the thermostat to the wall or outlet

box with screws through the two mounting holes at
the middle of the device.

The sheet metal 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.

0 Exactly level the thermostat using a spirit level or

plumb line. Tighten the two mounting screws at the

middle of the device.
0 Install two screws in top mounting holes and tighten.
0 Replace the thermostat cover.

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