Honeywell Q674L User Manual

X-XX UL
INSTALLATION INSTRUCTIONS
®U.S. Registered Trademark
Copyright © 1997 Honeywell Inc. • • All Rights Reserved
T874R Thermostats and Q674L Subbases
Installation Instructions for the Trained Service Technician.
APPLICATION
The T874R Thermostat and Q674L Subbase provide 24 to 30 Vac control of 2-stage heating and 1-stage cool-ing heat
pump systems with manual changeover. Q674L Subbase provides EM.HT.-HEAT-OFF-COOL system switching and
AUTO-ON fan switching. See Table 1 for specific T874R/Q674L combinations.
Table 1. Thermostat/Subbase Specifications.
Thermostat/
Subbase
Package
Thermostat/
Subbase
Model
Numbers
LED
Indication Changeover Comments
See
Fig.
Y594R1243 T874R1152/
Q674L1207
AUX.HT.,
EM. HT.
Manual Cool
TRADELINE
®
; adjustable stage 2
heat anticipation. Fixed anticipation
in stage 1. Auto fan in EM.HT.
6
Y594R1300 T874R1475/
Q674L1520
AUX.HT.,
EM. HT.
a
Manual Heat
or Cool
TRADELINE
®
; fixed heat
anticipation. Auto fan in EM.HT.
7
Y594R1425 T874R1616/
Q674L1587
AUX.HT.,
EM. HT.,
CHECK
Manual Heat
or Cool
SUPER TRADELINE
®
; fixed heat
anticipation. Factory installed jumper
across W1 and Y1. Auto fan in
EM.HT.
8
Y594R1615 T874R1822/
Q674L1710
AUX.HT.,
EM. HT.,
CHECK
Manual Heat
or Cool
TRADELINE
®
; fixed heat
anticipation. Auto fan in EM.HT.
10
Y594R1664 T874R1871/
Q674L1736
EM. HT. Manual Cool
TRADELINE
®
; exact replacement
for York model no. 2TH11702224.
9
Y594R1672 T874R1889/
Q674L1736
EM. HT. Manual Cool
TRADELINE
®
; exact replacement
for York model nos. 2TH11702324
and 6TH11702224.
11
Y594R1698
b
T874R1905/
Q674L1777
EM. HT. Manual Cool
TRADELINE
®
; exact replacement
for York model nos. 2TH11702324
and 6TH11702224. Includes
C815A1054 Outdoor Thermistor.
11
Y594R1706
b
T874R1913/
Q674L1777
EM. HT. Manual Cool
TRADELINE
®
; exact replacement
for York model no. 2TH11702224.
9
Y594R1763 T874R1954/
Q674L1827
AUX.HT.,
EM. HT.
a
Manual Cool Requires C815A Outdoor Thermister
for outdoor reset. Fixed stage 1 heat
anticipation. No heat anticipation in
stage 2 heat. Auto fan in EM.HT.
Replaces Y594R1136.
5
Y594R1797 T874R1988/
Q674L1868
AUX.HT.,
EM.HT.
Manual Heat
or Cool
TRADELINE
®
12
a
EM.HT. LED also shows compressor malfunction.
b
Premier White® color.
69-0392-9

Honeywell Q674L Specifications

General

Brand	Honeywell
Model	Q674L
Category	Thermostat
Language	English

Summary

Application Overview

Operation Details

Safety Precautions

Critical safety warnings to prevent electrical shock or equipment damage during operation.

Important Operational Notes

Key considerations and notes for proper system operation.

Recycling and Disposal

Guidelines for safe disposal of mercury-containing controls.

Installation Guide

Subbase Mounting

Instructions for mounting the subbase on a wall or outlet box.

Subbase Wiring

Steps for connecting system wires to the subbase terminals.

Thermostat Mounting

Procedure for attaching the thermostat to the installed subbase.

System Settings

General Installation Caution

Warning against applying jumpers across gas valve terminals.

Heat Anticipator Adjustment

Setting the heat anticipator for optimal heating control.

Temperature Setpoint

Adjusting the temperature control lever for comfort.

Subbase Switch Configuration

Setting system and fan switches on the subbase.

System Checkout Procedures

Heating System Verification

Testing heating operation by adjusting the thermostat setpoint.

Cooling System Verification

Testing cooling operation by adjusting the thermostat setpoint.

Emergency Heat Testing

Verifying emergency heat function and LED indicator.

Fan Operation Check

Confirming fan behavior in continuous and auto modes.

Calibration and Adjustment

Thermostat Factory Calibration

Note on factory calibration of the thermostat.

Thermometer Accuracy Check

Procedure to adjust the thermometer if readings are inaccurate.