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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
163 60-2485—8
Fig. 152. Schematic and hookup of T874D with Q674F. Used in standard applications.
Fig. 153. Schematic and hookup of T874G with Q674F. Used in heat pump applications.
OFF
ON
SYSTEM
SWITCH
FAN SWITCH
1
2
3
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
M8377
HEAT RELAY 2
COMPRESSOR
CONTRACTOR 1
EM. HEAT
LED (RED)
EM. HT.
HEAT
AUTO
HEAT RELAY
COMPRESSOR
CONTRACTOR 2
AUTO
H1 ANTICIPATOR
H2 ANTICIPATOR
C2 ANTICIPATOR
C1
RISE
RISE
W1
FALL
H1
FALL
H2
RC
Y1
G
1
Y2
X2
O
B
X1
E
RH
FAN RELAY
EM. HT. RELAY
L1
(HOT)
L2
1
L1
(HOT)
L2
1
2
FACTORY SUPPLIED FIELD INSTALLED JUMPER TO E-X2 FOR CONSTANT POWER TO EM HT LIGHT IN EM HT POSITION.
3
OPTIONAL FIELDWARE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER.
6
C1 ANTICIPATOR
C2
11
10
W2
8
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
COOL
9
4
OFF
COOL
OUTDOOR
THERMOSTAT
FAN
SWITCH
ON
SYSTEM
SWITCH
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
M8381
AUX. HT. RELAY
CONTACT
AUX. HT. RELAY
4
EM. HT. LED
(RED)
EM. HT.
HEAT
AUTO
COOL CHANGEOVER
VALVE
FAN RELAY
COMPRESSOR
CONTACTOR
AUTO
H1
ANTICIPATOR
H2 ANTICIPATOR
C1 ANTICIPATOR
C1
RISE
RISE
EM. HT.
RELAY
6
O
9
10
R
CO
FALL
H1
FALL
H2
W2
L1
(HOT)
L2
1
G
1
2
E
X
THERMOSTAT
SUBBASE SYSTEM COMPONENTS
8
Y