4
WIRING
TH
TR
MV HI
MV COM
MV LO
GND
HLO
HLI
PSO
PSI
C
R
G
W
Y
Y
W
G
R
THERMOSTAT
2 STAGE
GAS
VALVE
HIGH LIMIT
(N. C.)
ROLLOUT
(N. C.)
AUX. HIGH
LIMIT (N. C.)
PRESSURE SWITCH (N. O.)
COMPRESSOR
CONTACTOR
ELECTRONIC
AIR CLEANER
CIRCULATOR
BLOWER
50M56
24 VAC
120 VAC
24 VAC CLASS II
TRANSFORMER
HOT
(LINE)
NEUTRAL
(LINE)
FS
FLAME
SENSOR
PROBE
TH
TR
RO OUT
RO IN
TYPICAL SYSTEM WIRING DIAGRAM
Low Voltage (24 VAC)
Line Voltage (120 VAC)
LEGEND
N. C. = Normally closed switch
N. O. = Normally open switch
1 STAGE
GAS
VALVE
[4-Pin Connector]
[12-Pin Connector]
IGNITOR
INDUCER
IGN
IGN-N
IND
IND-N
LINE N
XFMR N
EAC N
CIR N
PARK
EAC
XFMR
LINE
PARK
HI HEAT
LO HEAT
COOL
12-Pin Connector
HLO
PSO
HLI
PSI
GND
TH
TR
MV
LO
RO
OUT
RO
IN
MV
COM
MV
HI
4-Pin Connector
IND
IGN
IND
N
IGN
N
