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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
71 60-2485—8
Table 9. Q674 Subbase Cross Reference.
Model
Number
Fig.
No. Description
Q674 Trade
Replacement Remarks
Q674A System: HEAT-AUTO-COOL; Fan: AUTO-ON
A1001 71 Standard OEM. Q674A1019
A1019 71 TRADELINE® model; used with T874A-D. Q674A1019
A1035 71 Obsolete
. Trane part no. BAS-0435; used with T874A-D. Q674A1019
A1043 71 Honeywell logo; TRADELINE model; Q674A1019
A1050 71 Obsolete
. Standard OEM. Q674A1043
Q674B System: HEAT-OFF-COOL; Fan: AUTO-ON
B1000 45 Standard OEM; used with T874C1570, C1695, C1703,
D1843; used in Y594C1363.
Q674B1034
B1018 44 Standard OEM; used with T874B1035, D1082; used in
Y594B1026, D1016.
Q674B1018
B1026 45 Obsolete
. System: HEAT-OFF-RESET-COOL. Q674B1034
B1034 45 TRADELINE Q674B1034
B1042 47 Obsolete
. Used with T874R1004, R1509; used in
Y594R1029, R1334.
Y594R1243
a
Wiring differences (old=new):
W1=W2.
B1059 45 Obsolete
. Factory installed RC-RH jumper; used with
T874C1059; used in Y594C1256.
Q674B1034 Field wire RC-RH.
B1075 46 Auto fan in heating and cooling mode; used with
T874B1035, C1000, D1082; used in Y594D1040.
Q674B1075
B1083 51 Obsolete
. Carrier part no. HH93AZ178; factory
installed RC-RH jumper.
Q674B1075
a
One system transformer only.
B1091 45 Obsolete
. Carrier part no. HH93AZ184; factory
installed RC-RH jumper.
Q674B1034
B1109 47 Obsolete
. Addison heat pump; used with T874R1012.
Y594R1243
a
Wiring differences (old=new):
W1=W2.
B1117 44 Obsolete
. Carrier part no. HH93AZ180; factory
installed RC-RH jumper.
Q674B1018
a
B1125 53 Obsolete. York part no. 2TB04700324A; used with
T874D1041.
Q674B1075
a
Jumper RC-RH; replacement
has no LOCKOUT LED.
B1133 48 Obsolete
. Includes FILTER LED; used with
T874D1082; used in Y594D1156.
Q674B1018
B1141 51 Trane part no. BAY28X185; automatic fan operation in
heat and cool mode.
Q674B1075 Set T874 H1 anticipator for
combined load of heat relay
and fan relay.
B1158 50 Obsolete
. Used with T874G1071. T874C1018/
Q674B1018
a
W1-Y1 and RH-RC jumpers
required.
B1166 249 Carrier part no. HH93AZ179; factory installed RC-RH
jumper; LOCKOUT LED; used with T874C1075
(HH07AT170).
Y594C1421 or
Q674B1075
a
Replacement only requires
one transformer and has no
LOCKOUT LED.
B1190 52 Obsolete. Wards special; factory installed RH-RC and
F-W3 jumpers; used with T874C1372.
Gas Furnace:
Q674B1034
Electric Furnace:
Q674B1075
B1208 187 Obsolete
. Used with T874C1422. None
B1216 54 Used with T874W1015 and C815A1005; used in
Y594W1014.
Q674B1216
B1224 49 Obsolete
. Lennox part no. 25F7301; four LEDs; used
with T874C1430.
Q674B1034 Replacement has no LEDs.
a
Both the thermostat and subbase must be replaced.