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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
60-2485—8188
Fig. 189. Schematic and hookup of T874F with Q674D. Used in standard applications.
Fig. 190. Schematic and hookup of T874C with Q674L. Used in heat pump applications.
H1
FALL
M3960
Y1
H2
W1
1
4
6
8
9
10
FALL
Y2
11
W2
RH
B
R
Y
L1
L2
RC
5
ANTICIPATOR
M839
MOTOR
THERMOSTAT SUBBASE SYSTEM COMPONENTS
NO
FAN
SWITCH
NO
SYSTEM
SWITCH
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.
OPTIONAL REMOVABLE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER.
WIRE JUMPER FOR SERVICE LIGHT.
M3978
AUTO
ON
FAN
SWITCH
L
F
X
A
Y
H2
E
M
C1
ANTICIPATOR
C1
RISE
EM. HT. LED
(YELLOW)
HEAT
2
3
4
6
8
10
SERVICE
LED (RED)
COMPRESSOR
CONTACTOR
FALL
O. D. S.
H2
ANTICIPATOR
THERMOSTAT SUBBASE SYSTEM COMPONENTS
COOL
OG
COOL CHANGEOVER
VALVE
C815A
OUTDOOR THERMISTOR
5
1
7
R
VR
V
EM. HT.
EM. HT. RELAY
IN STAT
HI PR
SERVICE
RELAY
ELEC. HT. RELAY
ELEC. HT. RELAY
RESET
2
3
3
2
1
L1
(HOT)
L2