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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
177 60-2485—8
Fig. 170. Schematic and hookup of T874G with Q674F. Used in heat pump applications.
H1
FALL
RISE
CO
L1
(HOT)
L2
1
C1
RISE
1
2
3
3
2
POWER SUPPLY. PROVIDE DISCONNECT
MEANS AND OVERLOAD PROTECTION AS REQUIRED.
ON SOME MODELS, Y TERMINAL MAY BE LABELED Y1.
EMERGENCY HEAT RUNS CONTINUOUSLY WHEN SWITCH IN IN EM. HT. POSITION.
C1 ANTICIPATOR
H1 ANTICIPATOR
FAN SWITCH
AUTO
ON
SYSTEM
SWITCH
AUTO
HEAT
OFF
COOL
2
4
8
9
10
W2
X
L
B
R
G
Y
AUX. HT. RELAY
FAN RELAY
EM. HT.
RELAY
B RELAY
M5987A
THERMOSTAT SUBBASE SYSTEM COMPONENTS
COMPRESSOR
CONTACTOR
EM. HT.
EM. HT.
LED (RED)
AUX. HT.
LED (GREEN)
H2
FALL
H2
ANTICIPATOR
3
5
W3
W1
W3 RELAY
W1 RELAY
COOL
CHANGEOVER
VALVE
COMPRESSOR
FAULT
E
O
6