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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
143 60-2485—8
Fig. 123. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
H2
FALL
H1
FALL
C1
L1
(HOT)
L2
1
2
2
1
2
POWER SUPPLY. PROVIDE
DISCONNECT MEANS AND
OVERLOAD PROTECTION
AS REQUIRED.
CONNECT CHANGEOVER
RELAY TO B FOR HEAT
CHANGEOVER, TO O FOR
COOL CHANGEOVER.
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
LACO
CHP
ODT 1
RTD 1
EHR 1
RTD 2
ODT 2
EHR 2
RTD 3
COMPRESSOR
MONITOR
R
L
X
W2
G
O
E
Y
B
HEAT
CHANGEOVER VALVE
COMPRESSOR
CONTACTOR
EM. HT. RELAY
COOL
CHANGEOVER VALVE
FAN RELAY
RTD 1
RD
10
8
H2
ANTICIPATOR
6
5
4
3
2
H1/C1
ANTICIAPTOR
FAN
SWITCH
AUTO
ON
SYSTEM
SWITCH
EM. HT.
HEAT
OFF
COOL
EM. HT.
LED (RED)
AUX. HT.
LED
(GREEN)
M1030A