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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
123 60-2485—8
Fig. 97. Schematic and hookup of T874P with Q674C. Used in heat pump applications.
Fig. 98. Schematic and hookup of T874D with Q674E. Used in standard applications.
H2
FALL
H1
RISE
CO
L1
(HOT)
L2
1
C1
RISE
COMPRESSOR CONTACTOR
FAN RELAY
CLOSED-DAY
OPEN-NITE
B RELAY
SERVICE
LED (RED)
OVERRIDE
LED (RED)
FAN
SWITCH
AUTO
ON
H1
ANTICIPATOR
SYSTEM SWITCH
JUMPER
COOL CHANGEOVER VALVE
OVERRIDE
AUTO
OFF
C1 ANTICIPATOR
1
2
3
4
5
6
8
9
10
W
P
S
X
L
B
R
C
G
Y
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
JUMPER HONEYWELL SUPPLIED, FIELD INSTALLED.
H2 MAKE OFFEST 8˚ F BELOW H1 MAKE.
3
2
1
2
3
M100A
THERMOSTAT
SUBBASE SYSTEM COMPONENTS
COMPRESSURE FAILURE
Y1
RC
1
M5106A
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
B
Y2
W2
RH
H1 ANTICIPATOR
H2 ANTICIPATOR
C1
RISE
H1
FALL
FALL
H2
C2
RISE
C2 ANTICIPATOR
C1 ANTICIPATOR
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
T874A IS SINGLE-STAGE (NO W2 OR Y2).
O
A
AUTO
ON
FAN
SWITCH
SYSTEM
SWITCH
OFF
CHANGEOVER
RELAY
HEAT RELAY 1
COMPRESSOR
CONTACTOR 1
HEAT RELAY 2
L1
(HOT)
L2
1
COMPRESSOR
CONTACTOR 2
AUTO
HEAT
SERVICE
LED (RED)
W1
G
L1
(HOT)
1
L2
CHANGEOVER
RELAY
FAN RELAY
2
SYSTEM MONITOR
COOL
1
6
9
10
11
4
8
2