Honeywell T874 - Page 159

T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES
159 60-2485—8
Fig. 147. Schematic and hookup of T874G with Q674F. Used in heat pump applications.
Fig. 148. Schematic and hookup of T874G with Q674F. Used in heat pump applications.
H1
FALL
1
G
A
X
W2
R
AUTO
COOL
SYSTEM
SWITCH
H1
ANTICIPATOR
AUTO
ON
FAN
SWITCH
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
CONNECT TO Y OR W TERMINAL WITH FACTORY INSTALLED JUMPER.
M7024
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
4
8
9
10
H2
ANTICIPATOR
O
L
2
3
6
EM. HT.
HEAT
OFF
Y
H2
FALL
CO
RISE
C1
ANTICIPATOR
RISE
C1
L1
(HOT)
L2
1
2
S
W3
E
T
MODE SIGNAL
COOL
CHANGEOVER
VALVE
COMPRESSOR
CONTACTOR
EM. HT. RELAY
HEAT RELAY 1
HEAT RELAY 2
FAN RELAY
MODE SIGNAL
5
AUX. HT.
LED (GRN)
EM. HT.
LED (YEL)
SERVICE
LED (RED)
2
2
3
JUMPER FACTORY INSTALLED.
3
OFF
COOL
DEFROST
RELAY
FAN
SWITCH
ON
SYSTEM
SWITCH
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
M8382
AUX. HT. RELAY
EM. HT. RELAY
4
EM. HT.
LED
(RED)
EM. HT.
HEAT
AUTO
COOL CHANGEOVER
VALVE
BLOWER SPEED
RELAY
DEFROST
RELAY
BLOWER RELAY
COOL
CONTRACTOR
LOCKOUT
THERMOSTAT
AUTO
E
H1 ANTICIPATOR
H2 ANTICIPATOR
C1
ANTICIPATOR
C1
RISE
RISE
6
O
8
10
R
CO
FALL
H1
FALL
H2
W2
L1
(HOT)
L2
1
G
1
Y
C
THERMOSTAT
SUBBASE
SYSTEM COMPONENTS
9
2