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T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
181 60-2485—8
Fig. 177. Schematic and hookup of T874G,H with Q674C. Used in standard applications.
Fig. 178. Schematic and hookup of T874N with Q674F. Used in heat pump applications.
H1
FALL
L1
(HOT)
L2
1
FALL
M114C
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
USE EITHER 'B' OR 'O' ONLY FOR SYSTEM CHANGEOVER. 0.8A AT 30 VAC MAXIMUM LOAD CURRENT.
SECOND STAGE HEAT MAKES 12
o
F (7
o
C) AFTER FIRST STAGE HEAT TO PROVIDE SETBACK
1
2
2
THERMOSTAT
SUBBASE SYSTEM COMPONENTS
1
R2
R1
B
O
Y
G
FAN
SWITCH
AUTO
ON
SYSTEM SWITCH
RESET LED
(RED)
OFF
AUTO
C1
H2
H1 ANTICIPATOR
FAN RELAY
COOL
CHANGEOVER VALVE
HEAT CHANGEOVER
VALVE
COMPRESSOR
CONTACTOR
C1 ANTICIPATOR
RISE
2
3
3
RISE
CO
4
6
7
8
9
10
LOCKOUT
(RESET) RELAY
X
H2
FALL
C0
RISE
H1
FALL
M18623
H1 ANTICIPATOR
H2 ANTICIPATOR
C1 ANTICIPATOR
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
1
1
3
4
6
8
9
10
K
L
W2
R
G
W1
SYSTEM
SWITCH
HEAT
EM.HT.
OFF
COOL
AUTO
ON
AUTO
FAN
SWITCH
SERVICE
LED (RED)
EM, HT. LED
(YELLOW)
AUX.HT. RELAY
FAN RELAY
CHANGEOVER RELAY
COMPRESSOR RELAY
EM.HT. RELAY
C
X
THERMOSTAT SUBBASE
SYSTEM COMPONENTS
L1
(HOT)
L2
1