Honeywell T874G User Manual

T874G Thermostats
and Q674F,J Subbases
for Heat Pump Systems
J.H. • Rev. 7-94 • • ©Honeywell Inc. 1994 • Form Number 69-0435—10
TRADELINE
®
TABLE 1—THERMOSTAT/SUBBASE SPECIFICATIONS.
Application
The T874G Thermostats and Q674F,J Subbases pro-
vide 24 to 30 Vac control of 2-stage heating and 1-stage cool-
ing heat pump systems with automatic changeover. Stage 1
heat and cool anticipation is fixed voltage type; stage 2 heat
anticipation is adjustable (except as noted). See Table 1 for
specific T874G/Q674F,J combinations and specifications.
Installation Instructions for the Trained Service Technician.
Thermostat/
Subbase
Thermostat/
Subbase
Model LED
Switching
See
Package Numbers Indication
System Fan Changeover Comments
Fig.
Y594G1252 T874G1246/
Q674F1212
AUX.HT.,
EM.HT.
a
EM.HT.-OFF-
HEAT-AUTO-
COOL
AUTO-
ON
AUTO,
COOL
TRADELINE
®
5
— T874G1246/
Q674F1410
AUX.HT.,
EM.HT.
a
EM.HT.
b
-OFF-
HEAT-AUTO-
COOL
AUTO-
ON
AUTO,
COOL
Separate W1 and Y1
terminals; TRADELINE
®
subbase.
6
Y594G1419 T874G1642/
Q674F1444
AUX.HT.,
EM.HT.,
CHECK
OFF-EM.HT.-
HEAT-AUTO-
COOL
AUTO-
ON
AUTO,
HEAT OR
COOL
SUPER TRADELINE
®
;
includes factory-installed
jumper across W1 and Y1;
fixed stage 2 heat anticipation.
7
Y594G1476
c
T874G1741/
Q674F1477
Isolated CHECK LED
includes jumper for connecting
X2 terminal to X or R for
power.
Y594G1534
d
T874G1824/
Q674F1477
Y594G1526 T874G1626/
Q674F1436
AUX.HT.,
EM.HT.
OFF-EM.HT.-
HEAT-AUTO-
COOL
AUTO-
ON
AUTO,
HEAT
TRADELINE
®
8
— T874D1165
or
T874E1016/
Q674F1543
(RED)
e
OFF-EM.HT.-
HEAT-AUTO-
COOL
AUTO-
ON
AUTO TRADELINE
®
subbase; exact
replacement for York model
no. 2TB04700524. Thermostat
not included; order separately.
9
Y594G1567 T874G1865/
Q674J1209
EM.HT. EM.HT.-
AUTO-OFF
AUTO-
ON
AUTO,
COOL
TRADELINE
®
; exact
replacement for York model
nos. 2TH11702424 and
6TH11702424.
10
Y594G1575
c
T874G1873/
Q674J1225
EM.HT. EM.HT.-
AUTO-OFF
AUTO-
ON
AUTO,
COOL
TRADELINE
®
; exact
replacement for York model
nos. 2TH11702424 and
6TH11702424.
10
Y594G1633 T874G1972/
Q674F1584
AUX.HT.,
EM.HT.
OFF-EM.HT.-
HEAT-AUTO-
COOL
AUTO-
ON
AUTO,
HEAT OR
COOL
TRADELINE
®
11
a
EM.HT. also shows compressor malfunction.
b
When switch is in EM. HT. position, the emergency heat will operate continuously until system switch is moved to another position.
c
Thermostat is white and subbase is gray.
d
Sold only in Australia; degrees C.
e
LED indicator is not labeled but may be connected per user's requirements. See Fig. 9.
M3375

Honeywell T874G Specifications

General

Brand	Honeywell
Model	T874G
Category	Thermostat
Language	English

Summary

Application Overview

Installation Guide

Installation Location

Proper placement for thermostat installation to ensure accurate readings and performance.

Subbase Mounting Procedures

Instructions for securely attaching the subbase to outlet boxes or walls.

Subbase Wiring Connections

Detailed steps for making electrical connections to the subbase terminals.

Thermostat Mounting

Steps for attaching the thermostat unit to the installed subbase.

Temperature Setting Adjustments

Guidelines for setting heating and cooling temperature levers.

Subbase System and Fan Settings

Understanding the function of system and fan switch positions.

System Checkout Procedures

Heating System Checkout

Verifying proper operation of the heating stages and fan.

Cooling System Checkout

Testing the cooling system and fan functionality.

Emergency Heat Checkout

Confirming the emergency heat operation and associated LED.

Fan Operation Checkout

Checking continuous and automatic fan operation.

Device Calibration

Thermostat Calibration

Information on factory calibration and field adjustments.

Thermometer Calibration Procedure

Steps to calibrate the thermostat's internal thermometer.