69-0268—11 6

T874G,R MULTISTAGE HEAT PUMP THERMOSTATS AND Q674F,J,L SUBBASES
H2
FALL
H1
FALL
C1
L1
(HOT)
L2
1
1
2
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
REMOVE JUMPER FOR INDEPENDENT CONTROL OF W1 AND E TERMINALS.
THERMOSTAT SUBBASE SYSTEM COMPONENTS
H1/C1
ANTICIPATOR
H2
ANTICIPATOR
RESET
SYSTEM
SWITCH
FAN
SWITCH
AUTO
ON
OFF
HEAT
EM. HT.
COOL
COMPRESSOR
CONTACTOR
FAN RELAY
M1858
2
3
4
5
6
11
12
Y
T
C
X
E
R
G
O
COOL CHANGEOVER
VALVE
3R
SEQ 1
SEQ 2
EM. HT. RELAY
4R
4R
5R
HPS 4R
4R
C815A
OUTDOOR
THERMISTOR
SYSTEM
LED
(GREEN)
EM. HT.
LED
(RED)
W1
AUX. HT.
LED
(YELLOW)

Fig. 6. Internal schematic and typical hookup for T874R/Q674L in heat pump system with outdoor reset. Includes

AUX. HT., EM. HT. and SYSTEM LEDs.

C1
H1 H1/C1
ANTICIPATOR
FALL
H2
ANTICIPATOR
L1
(HOT)L2
1
1 POWER SUPPLY. PROVIDE
DISCONNECT MEANS AND
OVERLOAD PROTECTION
AS REQUIRED.
H2
FALL
FAN RELAY
EM. HT. RELAY
B RELAY
AUXILIARY
HEAT RELAY
CHANGEOVER
RELAY
COMPRESSOR
RELAY
W2
G
O
E
EM. HT. RELAY
L
R
2
3
4
6
X
Y
B
AUXILIARY
HEAT
(GREEN)
EMERGENCY
HEAT
(RED)
26.5 VAC
TRANSFORMER
COOL
OFF
AUTO
ON
HEAT
EM. HT.
M6565

Fig. 7. Internal schematic and typical hookup for T874R/Q674L in heat pump system. Includes EM. HT and AUX.

HT. LEDs.