Honeywell T841A User manual

Honeywell

T841A

Heating-Cooling Thermostats

INSTALLATION INSTRUCTIONS

APPLICATION

The T841A Thermostats provide 24 Vac control of two-

stage heating and one-stage cooling in heat p mp

systems sing man al changeover.

The T841A provides EM.HT.-HEAT-OFF-COOL system

switching and AUTO-ON fan switching.

Test holes are provided on the front of the thermostat to

accommodate test meter leads witho t removing the

thermostat from the wall. Remove the cover of the

thermostat to expose test holes that are labeled to

correspond with the terminals on the back of the thermostat.

Table 1. Thermostat Feat res.

Thermostat Terminal

Designations LEDs A to Fan in

EM. HT. Fig re

N mbers

T841A W3, W2, Y, G, R, E, X, O, B, L AUX. HT., EM. HT., CHECK Yes 2

W3, W2, Y, G, R, E, X, O, B, L AUX. HT., EM. HT. Yes 3, 4

W, Y, R, T, F, G, X2, O, B EM. HT., AUX. HT. Yes 5

W3, W2, Y, G, R, E, X, O, B —Yes 6

W3, W2, Y, G, R, E, X, O, B EM. HT., AUX. HT. Yes 7

W2, W1, Y1, G, R, E, X, O, B EM. HT., AUX. HT. Yes 8

W3, W2, Y, G, R, E, X, O, B EM. HT., AUX. HT. Yes 9

W2, W1, Y, G, R, K, Z, X EM. HT., SERVICE No 10

W2, H, Y, G, R, E, X, A, O, B EM. HT., COMP. FAULT No 11

W, Y, G, R, X, O, B EM. HT., AUX. HT. Yes 12

W2, W1, Y1, G, R, E, X, O, B, L EM. HT., AUX. HT. Yes 13

W2, W1, Y, G, R, E, C/X, O, B, EM. HT., AUX. HT. Yes 14

W, Y, G, R, T, F, X2, O, B, U EM. HT., AUX. HT. Yes 15

W2, Y, G, R, E, B, X —Yes 16

OPERATION

The stages of heat make seq entially as the temperat re

drops. Make refers to the merc ry switch initiating a call for

heat or cool.

There is abo t 1 °F (0.6°C) between stages so the second

stage (a xiliary heat) makes only when the first stage

cannot handle the load. This 1°F is the interstage

differential.

The light emitting diode (LED) indicators on certain

thermostat models light when something specific happens

within the system. The AUX. HT. LED lights when a xiliary

heat (second stage heat) is operating d e to extremely

cold weather that req ires additional heat to s pplement

the heat p mp. When the red EM. HT. LED lights, the

emergency heat is operating ( s ally electric strip

heaters), beca se the homeowner has physically switched

to the EM. HT. position. When the red CHECK LED lights,

it indicates that something needs to be done to maintain

efficient system operation. See heating/cooling

man fact rer's instr ctions for specific meaning. When the

yellow COMP. FAULT LED lights, a compressor problem

req ires attention. When the yellow SERVICE LED lights,

see heating/cooling man fact rer's instr ctions for specific

meaning.

C o p y rig h t © 1 99 8 H o neyw ell Inc. All R ights R e se r v e d 69-1218

T841A HEATING-COOLING THERMOSTATS

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

-SYSTEM SWITCH FAN SWITCH

THERMOMETER

SET POINT

SCALE

- LED (UP

TO THREE) MOUNTING

HOLES (4) L WIRING TERMINAL 1

(UP TO 12)

COVER

Fig. 1. External view of T841A.

® RECYCLING NOTICE

This control contains merc ry in a sealed t be. Do

ntplace control in the trash at the end of its sef l

life.

If this control is replacing a control that contains

merc ry in a sealed t be, do ntplace yo r old

control in the trash.

Contact yo r local waste management a thority for

instr ctions regarding recycling and the proper

disposal of this control, or any control containing

merc ry in a sealed t be.

INSTALLATION

When Installing this Prod ct...

1. Read these instr ctions caref lly. Fail re to follow

them co ld damage the prod ct or ca se a

hazardo s condition.

2. Check the ratings given in the instr ctions and on

the prod ct to make s re the prod ct is s itable for

yo r application.

3. Installer m st be a trained, experienced service

technician.

4. After installation is complete, check o t prod ct

operation as provided in these instr ctions.

A CAUTION

1. Disconnect power s pply before beginning

installation to prevent electrical shock or

eq ipment damage.

2. Do not short across coil terminals on relay.

This can b rn o t the thermostat heat

anticipator.

Location

Locate the thermostat abo t 5 ft (1.5m) above the floor in

an area with good circ lation at average temperat re.

Do not mo nt thermostat where it may be affected by:

— drafts, or dead spots behind doors and in corners.

— hot or cold air from d cts.

— radiant heat from s n or appliances.

— concealed pipes and chimneys.

— nheated ( ncooled) areas behind the thermostat, s ch

as an o tside wall.

This thermostat is a precision instr ment and was caref lly

adj sted at the factory. Handle it carefully.

Mo nting and Wiring

The T841 can be mo nted directly on a wall or a horizontal

o tlet box. Choose the method that best fits yo r

installation.

1. In replacement applications, check the existing

thermostat wiring for cracked or frayed ins lation.

Replace any wiring in poor condition. All wiring m st

comply with local codes and ordinances.

2. Grasp the thermostat cover at the top and bottom

with one hand. P ll o tward on the bottom edge of

the cover ntil it snaps free of the thermostat base.

Caref lly remove and save the packing material

s rro nding the merc ry switches.

3. R n 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 p shed

back into the wall later. Thread wires thro gh the

hole in the packing material saved in step 2.

Connect the wires to the terminals on the back of the

thermostat. See Fig. 2 thro gh 17.

4. Where applicable, set the second stage adj stable

heat anticipator to match the c rrent draw of the

primary heating control (see Heat Anticipator Setting

section).

5. P sh the excess wire back thro gh the hole and

pl g any opening with packing material to prevent

drafts that may affect thermostat performance.

69-1218 2

T841A HEATING-COOLING THERMOSTATS

6. Loosely sec re the therm ostat to the w all or o tlet

box w ith screw s thro gh the tw o m o nting holes in

the m iddle of the device. The sheetm etal screws

incl ded w ith the therm ostat are designed for se in

a plaster wall and anchors are not needed.

7. Level the therm ostat exactly sing a spirit level or

pl m b line. Tighten the two m o nting screw s at the

m iddle of the device.

8. Install two screw s in the top m o nting holes and

tighten.

IMPORTANT

An incorrectly leveled su ase will cause the

temperature control to deviate from setpoint. It is

not a cali ration pro lem.

9. R eplace the therm ostat cover.

ODT 1

(HOT)

CHANGEOVER

RELAY (COOL)

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

DO NOT JUMPER E TO W2 TERMINALS.

X TERMINAL MUST BE CONNECTED FOR PROPER OPERATION.

Fig. 2. Internal schematic and typical wiring diagram for T841A with CHECK, EM. HT., and AUX. HT. LEDs.

Provides both heat and cool changeover relay control. Common (X) wire m st be connected for proper operation.

369-1218

T841A HEATING-COOLING THERMOSTATS

L1 L2

(HOT)

Fig. 3. Internal schematic and typical wiring diagram for T841A with EM. HT. and AUX. HT. LEDs. Provides cool

changeover relay control only. Cool changeover (O) wire m st be connected for proper operation. Use L terminal

for compressor malf nction indication.

69-1218 4

T841A HEATING-COOLING THERMOSTATS

L1 L2

(HOT)

Fig. 4. Internal schematic and typical hook p for T841A with fan in Emergency Heat mode, 2-stage heat, 1-stage

cool, man al changeover.

L1 L2

(HOT)

Fi . 5. Internal schematic and typical wirin dia ram for T841A with EM. HT. and AUX. HT. LEDs. Provides

outdoor reset when used with C815 Thermistor. Provides cool chan eover relay control.

569-1218

T841A HEATING-COOLING THERMOSTATS

ODT 1

Fig. 6. Internal schematic and typical wiring diagram for T841A with EM. HT. LED. Provides both heat and cool

changeover relay control. Common (X) wire m st be connected for proper operation.

DISCONNECT MEANS AND

OVERLOAD PROTECTION

AS REQUIRED.

DO NOT JUMPER E TO W2 TERMINAL.

L1 L2

(HOT)

^W 3)-

•(W2)-

AUX. HT.

LED (GREEN)

a y

RTD 1 ODT 1

J- H hH-T-HH l~-|-|

EHR 1 RTD 2

ODT 2

m -TEEh

EHR 2 RTD

y r m a t

J-°-V H

------------

EM. HT.

LED (RED)

< X h

< c > - -

EM.HEAT

RELAY

-A V H — "

+ ° - V ° +

CHANGEOVER

VALVE (HEAT)

COMPRESSOR

CONTACTOR

+>VH—

CHANGEOVER

VALVE (COOL)

T<>v>|

Fi . 7. Internal schematic and typical wirin dia ram for T841A with AUX. HT. and EM. HT. LEDs. Provides both

heat and cool chan eover relay control. Common (X) wire must be connected for proper operation.

RID 1

CHP

M8505

69-1218 6

T841A HEATING-COOLING THERMOSTATS

HEAT RELAY 1

Fig. 8. Internal schematic and typical wiring diagram for T841A with AUX. HT. and EM. HT. LEDs. Provides both

heat and cool changeover relay control.

CHANGEOVER

VALVE (COOL)

Fi . 9. Internal schematic and typical wirin dia ram with AUX. HT. and EM. HT. LEDs. Provides both heat and

cool chan eover relay control.

769-1218

T841A HEATING-COOLING THERMOSTATS

FAN RELAY

Fig. 11. Internal schematic and typical wiring diagram for T841A with EM. HT. and COMP. FAULT LEDs.

Common (X) wire m st be connected for proper operation.

69-1218 8

T841A HEATING-COOLING THERMOSTATS

FAN REIAY

Fig. 12. Internal schematic and typical wiring diagram for T841A with EM. HT. and AUX. HT. LEDs.

(HOT) L2

/ K 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. M1103C

Fi . 13. Internal schematic and typical wirin dia ram for T841A with EM. HT. and AUX. HT. LEDs. Provides both

heat and cool chan eover relay control.

969-1218

? I > ^ > >

T841A HEATING-COOLING THERMOSTATS

L1 L2

Fig. 14. T841A with two a xiliary heat stages and AUX.HT. and EM.HT. LEDs. Provides a to fan in emergency heat.

Fig. 15. T841A with EM. HT. and AUX. HEAT LEDs. Provides o tdoor reset when sed with C815 Thermistor.

69-1218 10

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