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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
135 60-2485—8
Fig. 114. Schematic and hookup of T874D with Q674L. Used in heat pump applications.
L1
(HOT)
L2
1
F
E
SYSTEM
SWITCH
EM. HT.
HEAT
OFF
COOL
H1
ANTICIPATOR
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
M2
H1
FALL
R
AUTO
ON
FAN SWITCH
X
V
M
L
FAN
RELAY
H2
FALL
H2 ANTICIPATOR
C1
RISE
C2
RISE
C2
ANTICIPATOR
REMOVE FACTORY INSTALLED V-VR JUMPER WHEN CONNECTING
A TWO TRANSFORMER SYSTEM.
2
2
VR
Y
A
OUTDOOR
THERMOSTAT
HIGH SPEED
COMPRESSOR
CONTACTOR
LOW SPEED
COMPRESSOR
CONTACTOR
COOL
CHANGEOVER
VALVE
OUTDOOR
THERMOSTAT
SUPPL. ELEC.
HT. RELAY
SUPPL. ELEC.
HT. RELAY
EM. HT.
RELAY
C815A OUTDOOR
THERMISTOR
M2853
EM. HT. LED
(YELLOW)
EM. HT.
RELAY
SERVICE
LED (RED)
RESET
HEATER
C1
ANTICIPATOR
SERVICE
1
2
3
4
5
6
7
8
10
11
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS