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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
60-2485—8154
Fig. 138. Schematic and hookup of T874L with Q674B. Used in heat pump applications.
Fig. 139. Schematic and hookup of T874D with Q674F. Used in heat pump applications.
M103A
R1 NO2
S1 RELAY
S1 NC
SOLIENOID
RELAY
FAN RELAY
FAN SWITCH
AUTO
ON
J
S
G
R
C
H2
H1
O
AUX. HT. RELAY
COMPRESSOR
CONTACTOR
R1 NC1
R2 NO1
REVERSING
VALVE
R1 RELAY
SYSTEM SWITCH
HEAT
OFF
COOL
H1 ANTICIPATOR
H2 ANTICIPATOR
C1 ANTICIPATOR
10
9
8
7
5
4
3
2
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
FIELD REMOVABLE JUMPER
THERMOSTAT SUBBASE SYSTEM COMPONENTS
H2
FALL
H1
FALL
L1
(HOT)
L2
1
RISE
C1
2
2
1
H1
FALL
H2
FALL
C1
RISE
C2
RISE
L1
(HOT)
L2
1
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
H1 ANTICIPATOR
H2 ANTICIPATOR
C1 ANTICIPATOR
C2 ANTICIPATOR
SYSTEM
SWITCH
FAN
SWITCH
AUTO
ON
OFF
2 STG. HEAT
HEAT PUMP
AUX. HT.
COOL
FAN RELAY
AUX. HT. RELAY
COOL CHANGEOVER
VALVE
COMPRESSOR
CONTACTOR 1
COMPRESSOR
RELAY
COMPRESSOR
CONTACTOR 2
M4730
HEAT PUMP
LED (GREEN)
AUX. HT
LED (RED)
1
2
4
6
8
10
11
Y2
Y1
C
W2
W1
B
R
G
O