Download  Print this page

Honeywell T874H Installation Instructions Manual

Multistage thermostats and subbases
Hide thumbs
   

Advertisement

Quick Links

T874H,Q,W Multistage Thermostats and
APPLICATION
The T874H,Q,W Multistage Thermostats provide 24 to 30
Vac control for heating and cooling systems as listed in
Table 1.
Table 1. Heating and Cooling Stages.
Stage
Heating Stages
Cooling Stages
a
Plus a changeover stage that operates with cooling.
The Q674B,C,G,L Subbases provide wiring terminals,
system and fan switching, and mounting bases for T874
Multistage Thermostats as listed in Table 2.
Table 2. Switching Positions.
Q674
Model
System
B
Heat-Off-Cool
C
Off-Auto
G
Off-Auto
L
Em Ht-Heat-Off-Cool
OPERATION
On a two-stage or three-stage heat thermostat, the stages
make
of heat
sequentially as the temperature drops.
refers to the mercury switch initiating a call for heat or cool.
There are about 2 F (1 C) between the stages so that the
second stage makes only when the first stage can not
handle the load. About one degree later, the third stage
makes (T874W only). This degree difference is called the
interstage differential
.
Select models include LEDs (light-emitting diodes). The
LED lights to indicate a problem with the system; refer to
the system manufacturer instructions.
Copyright © 1996 Honeywell Inc. •
T874 Model
a
H
Q
1
1
1
Switch Positions
Fan
Auto-On
Auto-On
None
Auto-On
• All Rights Reserved
Q674B,C,G,L Subbases
When an LED lights, refer to this list for the meaning:
FILTER: clogged filter needs replacement.
EM. HT.: emergency heat is operating. The compressor
has failed, and the heat pump is not operating. The
LED lights when the homeowner places the system
switch in the EM. HT. position.
AUX. HT.: auxiliary heat is operating because the
weather is so cold that the heat pump alone cannot
handle the load.
SERVICE or CHECK: system needs to be checked.
W
See heating system instructions for specific
3
meaning.
2
LEDs are not field addable or replaceable.
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
control in the trash.
Contact your local waste management authority for
instructions regarding the recycling and the proper
disposal of this control, or of an old control
containing mercury in a sealed tube.
INSTALLATION
Make
When Installing this Product...
Read these instructions carefully. Failure to follow
them could damage the product or cause a hazard-
ous condition.
Check the ratings given in the instructions and on
the product to make sure the product is suitable for
your application.
Installer must be a trained, experienced service
technician.
After installation is complete, check out product
operation as provided in these instructions.
X-XX UL
INSTALLATION INSTRUCTIONS
not
place your old
69-0087-6

Advertisement

loading

  Related Manuals for Honeywell T874H

  Summary of Contents for Honeywell T874H

  • Page 1 FILTER: clogged filter needs replacement. EM. HT.: emergency heat is operating. The compressor The T874H,Q,W Multistage Thermostats provide 24 to 30 has failed, and the heat pump is not operating. The Vac control for heating and cooling systems as listed in LED lights when the homeowner places the system Table 1.
  • Page 2 Mounting and Wiring the Subbase Mount the subbase on a wall or horizontal outlet box. If you mount it on a vertical outlet box, order Honeywell part no. 193121A Adapter Assembly, which includes an adapter ring with two screws, and a cover plate to cover the marks on the wall.
  • Page 3 CONTACTOR RISE SYSTEM SWITCH SERVICE C1 ANTICIPATOR LED (YELLOW) AUTO RISE 24 VAC FILTER LED (RED) POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. M5902 Fig. 5. T874H/Q674C in heating-cooling system with SERVICE LED and FILTER LED. 69-0087—6...
  • Page 4 T874H,Q,W MULTISTAGE THERMOSTATS AND Q674B,C,G,L SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS H1 ANTICIPATOR NO FAN CHANGEOVER SWITCH RELAY FALL H2 ANTICIPATOR FAN RELAY FALL SYSTEM SWITCH COMPRESSOR CONTACTOR AUTO (HOT) POWER SUPPLY. PROVIDE DISCONNECT MEANS AND C1 ANTICIPATOR OVERLOAD PROTECTION AS REQUIRED.
  • Page 5 T874H,Q,W MULTISTAGE THERMOSTATS AND Q674B,C,G,L SUBBASES THERMOSTAT SUBBASE SYSTEM COMPONENTS (HOT) FALL H1 ANTICIPATOR C815A OD THERMISTOR H2 ANTICIPATOR AUX. HEAT RELAY FALL AUXILIARY FAN SWITCH HEAT LED (GREEN) H3 ANTICIPATOR AUTO FAN RELAY EMERGENCY HEAT LED FALL (RED) EM. HEAT RELAY...
  • Page 6: Mounting The Thermostat

    See Remove the thermostat cover by pulling the bottom Setting the Heat Anticipator section. T874H and edge of the cover upward until it snaps free of the T874W have fixed anticipation; the settings are cover clip.
  • Page 7 T874H,Q,W MULTISTAGE THERMOSTATS AND Q674B,C,G,L SUBBASES SETTING 4600 4400 4200 4000 C815A THERMISTOR RESISTANCE Setting the Heat Anticipator (T874Q Only) 3800 R = 400 ohms ± 10% AT 77°F (25°C) 3600 Set each heat anticipator to match its primary control...
  • Page 8 T874H,Q,W MULTISTAGE THERMOSTATS AND Q674B,C,G,L SUBBASES Fan (Select Models) NOTE: Hand heat offsets the thermometer Move the subbase system switch to OFF, and the fan reading. After making each adjustment, switch to ON. The fan runs continuously. When the fan...

This manual is also suitable for:

T874wQ674bQ674cT874qQ674gQ674l