69-0087—6
3
T874H,Q,W MULTISTAGE THERMOSTATS AND Q674B,C,G,L SUBBASES
FOR STRAIGHT
INSERTION–
STRIP 5/16 in. (8 mm)
FOR WRAPAROUND–
STRIP 7/16 in. (11 mm)
SUBBASE TERMINAL SCREW
M928
BARRIER
L1
(HOT)
L2 1
FAN RELAY
Y2
SYSTEM
SWITCH
OFF
AUTO
H1
ANTICIPATOR
CO
H1
FALL
1POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
SERVICE LED ON SELECT MODELS.
M3680A
AUTO
ON
FAN SWITCH
R
COMPRESSOR
CONTACTOR
COOL CHANGEOVER
VALVE
G
C1
RISE
RISE
O
C1
ANTICIPATOR
B
Y1
THERMOSTAT SUBBASE SYSTEM COMPONENTS
2
3
4
8
9
10
SERVICE LED
(YELLOW)
X
C
2
2
COMPRESSOR
FAULT
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
1POWER 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
Mounting C815A Thermistor (T874W only)

The T874W is used with the C815A Thermistor mounted in

the outdoor section. Locate it in an area where it can

measure the true outdoor ambient temperature. Avoid

mounting the C815A in an area where it is exposed to high

temperatures or direct sunlight. Refer to heat pump

equipment instructions for proper mounting.

Fig. 3. Wiring connections.

Fig. 4. T874H/Q674C in heating-cooling system.

Fig. 5. T874H/Q674C in heating-cooling system with SERVICE LED and FILTER LED.