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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
153 60-2485—8
Fig. 137. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
H2
FALL
H1
FALL
C1
LACO
CHP
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
THERMOSTAT SUBBASE
SYSTEM COMPONENTS
L1
(HOT)
L2
1
H1/C1
ANTICIPATOR
H2
ANTICIPATOR
SYSTEM
SWITCH
EM. HT.
HEAT
OFF
COOL
FAN SWITCH
AUTO
ON
AUX. HT.
LED (GREEN)
EM. HT.
LED
(RED)
CHECK
LED (RED)
COMP.
FAILURE
CHANGEOVER
VALVE (HEAT)
COMPRESSOR
CONTACTOR
Y
X
B
L
E
W2
R
G
W3
O
6
5
4
3
2
1
EM. HT. RELAY
RD
RTD 1
FAN RELAY
RTD 1 ODT 1
EHR 1
RTD 2
ODT 2
EHR 2
RDT 3
CHANGEOVER VALVE (COOL)
M105A
1