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Honeywell t841a Installation Instructions Manual
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Honeywell t841a Installation Instructions Manual

Honeywell t841a Installation Instructions Manual

Heating-cooling
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APPLICATION
The T841A Thermostats provide 24 Vac control of two-
stage heating and one-stage cooling in heat pump
systems using manual changeover.
The T841A provides EM.HT.-HEAT-OFF-COOL system
switching and AUTO-ON fan switching.
Thermostat
T841A
W3, W2, Y, G, R, E, X, O, B, L
W3, W2, Y, G, R, E, X, O, B, L
W, Y, R, T, F, G, X2, O, B
W3, W2, Y, G, R, E, X, O, B
W3, W2, Y, G, R, E, X, O, B
W2, W1, Y1, G, R, E, X, O, B
W3, W2, Y, G, R, E, X, O, B
W2, W1, Y, G, R, K, Z, X
W2, H, Y, G, R, E, X, A, O, B
W, Y, G, R, X, O, B
W2, W1, Y1, G, R, E, X, O, B, L
W2, W1, Y, G, R, E, C/X, O, B,
W, Y, G, R, T, F, X2, O, B, U
W2, Y, G, R, E, B, X
OPERATION
The 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
differential.
The light emitting diode (LED) indicators on certain
thermostat models light when something specific happens
C o p y r i g h t © 1 9 9 8 H o n e y w e l l In c .
Heating-Cooling Thermostats
Table 1. Thermostat Features.
Terminal
Designations
All R ig h t s R e s e r v e d
Test holes are provided on the front of the thermostat to
accommodate test meter leads without 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.
LEDs
AUX. HT., EM. HT., CHECK
AUX. HT., EM. HT.
EM. HT., AUX. HT.
—
EM. HT., AUX. HT.
EM. HT., AUX. HT.
EM. HT., AUX. HT.
EM. HT., SERVICE
EM. HT., COMP. FAULT
EM. HT., AUX. HT.
EM. HT., AUX. HT.
EM. HT., AUX. HT.
EM. HT., AUX. HT.
—
within the system. The AUX. HT. LED lights when auxiliary
heat (second stage heat) is operating due to extremely
cold weather that requires additional heat to supplement
the heat pump. When the red EM. HT. LED lights, the
emergency heat is operating (usually electric strip
heaters), because 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
manufacturer's instructions for specific meaning. When the
yellow COMP. FAULT LED lights, a compressor problem
requires attention. When the yellow SERVICE LED lights,
see heating/cooling manufacturer's instructions for specific
meaning.
Honeywell
T841A
INSTALLATION INSTRUCTIONS
Auto Fan in
EM. HT.
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
No
Yes
Yes
Yes
Yes
Yes
Figure
Numbers
2
3, 4
5
6
7
8
9
10
11
12
13
14
15
16
69-1218

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Summary of Contents for Honeywell t841a

  • Page 1 Remove the cover of the The T841A Thermostats provide 24 Vac control of two- thermostat to expose test holes that are labeled to stage heating and one-stage cooling in heat pump correspond with the terminals on the back of the thermostat.

  • Page 2: Installation

    FAN SWITCH -S Y S T E M SWITCH M OUNTING (UP TO 12) H OLES (4) Fig. 1. External view of T841A. Location ® RECYCLING NOTICE Locate the thermostat about 5 ft (1.5m) above the floor in This control contains mercury in a sealed tube. Do an area with good circulation at average temperature.
  • Page 3 X TERMINAL MUST BE CONNECTED FOR PROPER OPERATION. Fig. 2. Internal schematic and typical w iring diagram for T841A with CHECK, EM. HT., and AUX. HT. LEDs. Provides both heat and cool changeover relay control. Common (X) wire must be connected for proper operation.
  • Page 4 T841A HEATING-COOLING THERMOSTATS (HOT) Fig. 3. Internal schematic and typical w iring diagram fo r T841A with EM. HT. and AUX. HT. LEDs. Provides cool changeover relay control only. Cool changeover (O) wire must be connected for proper operation. Use L terminal fo r com pressor malfunction indication.
  • Page 5 T841A HEATING-COOLING THERMOSTATS (HOT) Fig. 4. Internal schematic and typical hookup fo r T841A with fan in Emergency Heat mode, 2-stage heat, 1-stage cool, manual changeover. (HOT) Fig. 5. Internal schematic and typical wiring diagram for T841A with EM. HT. and AUX. HT. LEDs. Provides outdoor reset when used with C815 Thermistor.
  • Page 6 T841A HEATING-COOLING THERMOSTATS ODT 1 Fig. 6. Internal schematic and typical wiring diagram fo r T841A with EM. HT. LED. Provides both heat and cool changeover relay control. Common (X) wire must be connected fo r proper operation. (HOT) RTD 1 ODT 1 J-°H hH-T-HH l~°-|-|...
  • Page 7 T841A HEATING-COOLING THERMOSTATS HEAT RELAY 1 Fig. 8. Internal schematic and typical w iring diagram fo r T841A with AUX. HT. and EM. HT. LEDs. Provides both heat and cool changeover relay control. CHANGEOVER VALVE (COOL) Fig. 9. Internal schematic and typical wiring diagram with AUX. HT. and EM. HT. LEDs. Provides both heat and cool changeover relay control.
  • Page 8 T841A HEATING-COOLING THERMOSTATS FAN RELAY Fig. 11. Internal schematic and typical wiring diagram fo r T841A with EM. HT. and COMP. FAULT LEDs. Common (X) wire must be connected fo r proper operation. 69-1218...
  • Page 9 T841A HEATING-COOLING THERMOSTATS FAN R E IA Y Fig. 12. Internal schematic and typical w iring diagram fo r T841A with EM. HT. and AUX. HT. LEDs. (HOT) 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.
  • Page 10 T841A HEATING-COOLING THERMOSTATS Fig. 14. T841A with two auxiliary heat stages and AUX.HT. and EM.HT. LEDs. Provides auto fan in emergency heat. Fig. 15. T841A with EM. HT. and AUX. HEAT LEDs. Provides outdoor reset when used with C815 Thermistor.

  • Page 11: Heat Anticipator Setting

    T841A HEATING-COOLING THERMOSTATS SUBBASE SYSTEM COM PONENTS THERMOSTAT __ A ___ ______A ________ ___ A _____ SYSTEM Fig. 16. Internal schematic and typical w iring diagram fo r T841A1720. Provides heat changeover relay control. SETTINGS Heat Anticipator Setting O n m o d e l s h o w n in F ig . 2, 3, 6 , 7, 8, 11, 1 4, 16 a n d 1 7 th e s e c o n d s ta g e h e a t a n tic ip a to r is a d ju s ta b le .
  • Page 12 T841A HEATING-COOLING THERMOSTATS Outdoor Reset Thermistor (Honeywell CHECKOUT C815A1005) Heating For system shown in Fig. 5, the thermistor must be used; if not, thermostat performance deviates radically from proper Move the system switch on the thermostat to HEAT and operation.