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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
60-2485—8158
Fig. 145. Schematic and hookup of T874G with Q674F. Used in heat pump applications.
Fig. 146. Schematic and hookup of T874D with Q674F. Used in heat pump applications.
OFF
COOL
OUTDOOR
THERMOSTAT
ON
SYSTEM
SWITCH
FAN
SWITCH
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
M8375
EM. HT. RELAY
TIME DELAY
FAN RELAY
4
EM. HT.
LED (RED)
EM. HT.
HEAT
AUTO
SUP. ELEC.
HT. RELAY
DEFROST
RELAY
COMPRESSOR
CONTACTOR
INTERNAL
THERMOSTAT
COOL CHANGEOVER
VALVE
HIGH
PRESSURE
SWITCH
OVERLOAD
AUTO
H1
ANTICIPATOR
H2
ANTICIPATOR
C1 ANTICIPATOR
C1
RISE
FALL
EM. HT. RELAY
6
V
9
8
10
CO
FALL
H1
FALL
H2
F
L2 (HOT) L1
1
Y
1
M
E
R
FAN RELAY
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
2
H1
FALL
Y1
G
W1
X
W2
R
AUTO
COOL
SYSTEM
SWITCH
H1 ANTICIPATOR
AUTO
ON
FAN
SWITCH
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
M7010
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
4
8
9
10
11
H2
ANTICIPATOR
SUPL.
HEAT
LED
(RED)
C
E
1
3
6
SUPL. HT.
HEAT
OFF
Y2
RVR RVR
EHR
EHR
COMPRESSOR
CONTACTOR 1
DFR 2
REVERSING
RELAY
FAN RELAY
L1
(HOT)
L2
1
ODT 3
HEAT
RELAY 2
HEAT RELAY 1
ODT 2
HEAT RELAY 3
SUPL. HT.
RELAY
DFR 2
COMPRESSOR
CONTACTOR 2
LPCO
H2
FALL
C1
RISE
C1
ANTICIPATOR
C2
ANTICIPATOR
RISE
C2
EHT