Honeywell
T874R Thermostats and Q674L Subbases
Installation Instructions for the Trained Service Technician.
TRADELINE•
INSTALLATION INSTRUCTIONS
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
Y594R1698b
T874R1905/
Q674L1777
EM. HT. Manual Cool
TRADELINE®; exact replacement
for York model nos. 2TH11702324
and 6TH11702224. Includes
C815A1054 Outdoor Thermistor.
11
Y594R1706b
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.
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Copyright © 1997 Honeywell Inc.
All Rights Reserved
69-0392-9
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