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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
219 60-2485—8
Fig. 241. Schematic and hookup of T874J with Q674L. Used in heat pump applications.
Fig. 242. Schematic and hookup of T874G with Q674C. Used in standard applications.
RISE
L1
(HOT)
L2
1
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
FAN SWITCH
AUTO
ON
SYSTEM
SWITCH
HEAT
OFF
COOL
2
3
4
5
6
8
9
10
11
12
R
X
E
L
C
G
W2
Y
P
O
FAN RELAY
HEAT
CHANGEOVER
VALVE NO. 1
HEAT
CHANGEOVER
VALVE NO. 1
HEAT
CHANGEOVER
VALVE NO. 2
HEAT
CHANGEOVER
VALVE NO. 2
HEAT
CHANGEOVER
VALVE NO. 3
M7742
THERMOSTAT SUBBASE SYSTEM COMPONENTS
COOL CHANGEOVER
VALVE
SUPL. HT.
CO
H1
H2
FALL
FALL
CO
C1
RISE
COMPRESSOR
CONTACTOR
P RELAY
X RELAY
O.D.T.
SUPL. HEAT
LED (RED)
H1
ANTICIPATOR
H2
ANTICIPATOR
C1
ANTICIPATOR
L1
(HOT)
L2
1
H2 ANTICIPATOR
H1 ANTICIPATOR
C1 ANTICIPATOR
FALL
H1
R
W2
W1
G
B
1
2
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
OVERRIDE IS MOMENTARY POSITION. SPRING RETURN TO (OFF)
UPON SWITCH RELEASE.
AUTO
ON
FAN
SWITCH
SYSTEM
SWITCH
AUTO
OVERRIDE
OFF
RISE
C1
C0
FALL
RISE
H2
Y
O
S1
S2
X
A
C
HEAT DAMPER
HEAT RELAY 1
FAN RELAY
HEAT RELAY 2
OVERRIDE
CIRCUIT
OVERRIDE
CIRCUIT
CHANGEOVER
VALVE
COMPRESSOR
RELAY
SERVICE
LED (RED)
ON LED (YEL)
M7212
1
4
6
8
9
10
THERMOSTAT
SUBBASE SYSTEM COMPONENTS