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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
39 60-2485—8
Table 7. Q672-Q674 Subbase Cross Reference.
Model Number Description
Q674 Trade
Replacement
a
Remarks
Q672A System: HEAT-AUTO-COOL, Fan: AUTO-ON
A1005 Standard OEM Q674A1019
A1013 TRADELINE Q674A1019
A1021 RC-RH jumper Q674A1019 RC-RH jumper required.
A1039 RC-RH jumper; Chek Lite Q674A1019 RC-RH jumper required.
Q672B System: HEAT-OFF-COOL, Fan: AUTO-ON
B1004 Standard OEM Q674B1034
B1012 Isolated G terminal. Q674B1018
B1020 System: HEAT-OFF-RESET-COOL Q674B1034 Used system off as reset position.
B1038 TRADELINE Q674B1034
B1046 Heat pump circuit; used with T872R1008. Y594R1425 Wiring differences (old=new):
W1=Y1, W=W2.
B1053 RC-RH jumper Q674B1034 RC-RH jumper required.
B1061 Chek Lite Q674B1034
B1079 Auto fan operation in heat and cool. Q674B1075
B1087 Carrier no. HH93AZ078; RC-RH jumper. Q674B1075
B1095 Carrier no. HH93AZ084; RC-RH jumper. Q674B1034
B1103 Addison; heat pump circuit; used with
T872R1016.
Y594R1425 Wiring differences (old=new):
W=W2; W1-Y1 jumper required.
B1111 Carrier no. HH93AZ080; isolated G terminal. Q674B1018
B1129 Trane special circuit; used with T872T1004. None
B1137 RC-RH jumper; isolated G terminal. Q674B1018 RC-RH jumper required.
B1145 Fedders special Q674B1034 RC-RH jumper required.
B1152 Fedders special; auto fan operation in heat
and cool.
Q674B1075
B1160 Lennox; heat pump circuit; used with
T872R1024; includes compressor lockout in
EM. HT.
Y594R1243 Wiring differences (old=new):
V-VR=R, M=Y, Y=W2, F=G, R=O.
B1178 General Electric no. AY28X107; auto fan
operation in heat and cool.
Q674B1075
B1186 Trane; isolated G terminal; Filter LED. Q674B1018
B1194 General Electric no. AY28X124; auto fan
operation in heat and cool.
Q674B1075 Set T874 stage-1 anticipator for
combined load of heat relay and fan
relay.
B1202 Lennox no. P-8-11223; heat pump circuit; used
with T872R1040.
Y594R1243 Wiring differences (old=new):
V-VR=R, M=Y, Y=W2, F=G, R=O.
B1210 None
B1228 General Electric no. BAY28X137; isolated
G terminal.
Q674B1018
B1236 Carrier no. HH-93AZ079; RC-RH jumper;
LOCKOUT LED indicates compressor lockout
switch activated.
Q674B1034 RC-RH jumper; LED cannot be
provided in TRADELINE model.
B1244 Friedrich; heat mode changeover; used with
T872R1115.
T874C1018/
Q674B1034
Wiring differences (old=new): C=no
connection; RC-RH and W1-Y1
jumpers required.
B1251 Used with T872W1035 and C815A1043. Y594W1014
a
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase.