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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
60-2485—8190
Fig. 193. Schematic and hookup of T874D with Q674E. Used in standard applications.
Fig. 194. Schematic and hookup of T874G with Q674F. Used in heat pump applications.
H1
FALL
L1
(HOT)
L2
1
RH
W1
W2
G
Y2
Y1
RC
HEAT RELAY 2
HEAT RELAY 1
OFF
HEAT
COOL
AUTO
AUTO
ON
SYSTEM
SWITCH
H1
ANTICIPATOR
C1 ANTICIPATOR
FAN
SWITCH
2
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
JUMPER RH, RC FOR SINGLE TRANSFORMER.
2
M3203B
L1
(HOT)
L2
1
FAN RELAY
O
CHANGEOVER
RELAY (COOL)
CHANGEOVER
RELAY (HEAT)
COMPRESSOR
CONTACTOR 2
COMPRESSOR
CONTACTOR 1
1
4
6
8
9
10
11
H2
FALL
C2 ANTICIPATOR
RISE
RISE
C1
C2
B
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
H2 ANTICIPATOR
L1
(HOT)
L2
1
FAN RELAY
SYSTEM
SWITCH
OFF
EM. HT.
H1
ANTICIPATOR
H1
FALL
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
M3977
AUTO
ON
FAN
SWITCH
R
G
CO
C
W1
W2
H2
RISE
E
Y1
C1
ANTICIPATOR
C1
RISE
EM. HT.
LED (RED)
HEAT
2
3
4
6
8
9
10
CHECK
LED
(GREEN)
COOL
CHANGEOVER VALVE
FALL
DR
HBTH
TDR 1
H2
ANTICIPATOR
THERMOSTAT SUBBASE SYSTEM COMPONENTS
AUTO
COOL
TDR 2
X
HPA
COMPRESSOR
CONTACTOR