Honeywell T874G Installation Instructions Manual page 4

Fig. 5—Internal schematic and typical wiring diagram for Y594G1252 (T874G1246/Q674F1212); auto
changeover in cooling.
THERMOSTAT
H1 ANTICIPATOR
H1 FALL
H2
ANTICIPATOR
H2
FALL
RISE
C1
ANTICIPATOR
CHANGEOVER
RISE
C1
1 POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
2 W3 TERMINAL ON SELECT MODELS.
Fig. 6—Internal schematic and typical wiring diagram for T874G1246/Q674F1410. Separate W1 and Y1
terminals can be jumpered together to form Y terminal.
THERMOSTAT
H1
FALL
H1 ANTICIPATOR
H2
ANTICIPATOR
FALL
H2
CO
C1 ANTICIPATOR
RISE
RISE
C1
POWER SUPPLY. PROVIDE DISCONNECT
1
MEANS AND OVERLOAD PROTECTION AS REQUIRED.
ON SOME MODELS, Y TERMINAL MAY BE LABELED Y1.
2
EMERGENCY HEAT RUNS CONTINUOUSLY WHEN SWITCH IN IN EM. HT. POSITION.
3
69-0435—10
2
FAN
SWITCH
3
AUTO
ON
4
5
6
SYSTEM
SWITCH
OFF
8
COOL
9
AUTO
HEAT
EM. HT.
10
2
FAN SWITCH
3
AUTO
4
ON
5
6
SYSTEM
SWITCH
OFF
EM. HT.
3
HEAT
8
AUTO
9
COOL
10
SUBBASE
AUX. HEAT
LED (GRN)
EM. HEAT
LED (RED)
SUBBASE
4
SYSTEM COMPONENTS
R
RTD1 OTD1
EHR1
2
W3
ODT2
W2
EHR2
RTD1
X
SYSTEM
MONITOR
L
G
RD
COOL
CHANGEOVER VALVE
O
E
COMPRESSOR
CONTACTOR
LACO
Y
SYSTEM COMPONENTS
W3
W1 RELAY
W3 RELAY
W1
B RELAY
B
FAN RELAY
G
R
AUX. HEAT RELAY
W2
AUX. HEAT
LED (GREEN)
X
EM. HT.
LED (RED)
COMPRESSOR
L
FAULT
E
COOL
CHANGEOVER EM. HT.
VALVE RELAY
O
COMPRESSOR
CONTACTOR
2
Y
L1
(HOT)
L2 1
RTD2
RTD3
FAN
RELAY
EM. HEAT
RELAY
CHP
M1589
L1
(HOT)
L2
1
M5987A