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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
127 60-2485—8
Fig. 103. Schematic and hookup of T874G with Q674L. Used in heat pump applications.
Fig. 104. Schematic and hookup of T874R with Q674L. Used in heat pump applications.
H2 ANTICIPATOR
1
SUPL. HT.
LED (RED)
M4665
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
1
SYSTEM COMPONENTSSUBBASETHERMOSTAT
L1
(HOT)
L2
1
H1
FALL
H2
FALL
2
4
6
O
G
R
W2
E
L
C
Y
CO
RISE
C1
RISE
8
9
10
H1 ANTICIPATOR
C1 ANTICIPATOR
SYSTEM
SWITCH
SUPL. HT.
COOL
OFF
FAN
SWITCH
AUTO
ON
FAN RELAY
COOL CHANGEOVER VALVE
OUTDOOR
THERMOSTAT
HEAT RELAY 1
HEAT RELAY
CONTACT 1
HEAT RELAY 2
HEAT RELAY
CONTACT 2
HEAT RELAY 3
2
COMPRESSOR
CONTACTOR 1
N.O. SWITCH – INSTALLER ADDED, TO LIGHT SUPL. HT. LED
WHEN COMPRESSOR OPERATION IS NOT NORMAL.
2
COMPRESSOR
FAULT
HEAT
1
1
2
L1
(HOT)
L2
2
POWER SUPPLY. PROVIDE DISCONNECT
MEANS AND OVERLOAD PROTECTION
AS REQUIRED.
OPTIONAL FIELD WIRE JUMPER TO CYCLE
AUXILIARY HEAT RELAY H1 INSTEAD OF
H2 (FASTER RESPONSE).
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
M4728
FAN
SWITCH
AUTO
ON
EM. HT. LED
(RED)
O
G
Y
H
W2
B
X
E
2
3
4
H2
FALL
H2 ANTICIPATOR
5
6
COM
EH
R8233B
YR
G
W
O
R
SYSTEM
SWITCH
OFF
HEAT
EM. HT.
COOL
H1
FALL
C1
EM. HT. RELAY
AUX. HT. RELAY
"B" RELAY
COMPRESSOR
CONTACTOR
ELEC. HT.
RELAY
H1/C1
ANTICIPATOR