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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
60-2485—8206
Fig. 220. Schematic and hookup of T874W with Q674C. Used in standard applications.
Fig. 221. Schematic and hookup of T874H with Q674C. Used in heat pump applications.
M5929
H1
FALL
L1
(HOT)
L2
1
THERMOSTAT
SUBBASE SYSTEM COMPONENTS
1
4
6
8
9
10
FAN
SWITCH
SYSTEM
SWITCH
AUTO
OFF
ON
AUTO
SERVICE
LED (RED)
COMPRESSOR CONTACTOR #2
HEAT RELAY #2
FAN RELAY
COMPRESSOR CONTACTOR #1
HEAT RELAY #3
H1
ANTICIPATOR
H2
ANTICIPATOR
C1
C2
RISE
RISE
FALL
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE.
1
CONTROL MODULE
H2
W3
Y1
G
R
W2
Y2
O
2
HEAT RELAY #1
W1
A
MOMENTARY
CIRCUIT
7
2
2
5
FALL
H3
SYSTEM MONITOR
M5902
L1
(HOT)
L2
1
Y2
X
R
COOL CHANGEOVER
VALVE
FAN SWITCH
ON
AUTO
SYSTEM
SWITCH
OFF
AUTO
H1
FALL
2
4
H1 ANTICIPATOR
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
C1
RISE
8
9
C1 ANTICIPATOR
3
10
CO
RISE
O
Y1
G
FAN RELAY
X2
C
X1
FILTER LED (RED)
SERVICE
LED (YELLOW)
COMPRESSOR
CONTACTOR
B
24 VAC