4
TH
TR
MV
MV
GND
FP
HLO
HLI
PS
C
R
TWIN*
TWIN*
G
W
Y
EAC N
HUM N
XFMR N
LINE N
CIR N
IGN
IND
HUM
EAC
XFMR
LINE
PARK
PARK
HEAT
COOL
IGNITOR
Y
W
G
R
THERMOSTAT
GAS
VALVE
HIGH LIMIT
(N. C.)
ROLLOUT
(N. C.)
AUX. HIGH
LIMIT (N. C.)
PRESSURE SWITCH (N. O.)
FLAME
SENSOR
PROBE
COMPRESSOR
CONTACTOR
ELECTRONIC
AIR CLEANER
HUMIDIFIER
INDUCER
CIRCULATOR
BLOWER
50A55
24 VAC
120 VAC
24 VAC CLASS II
TRANSFORMER
HOT
(LINE)
NEUTRAL
(LINE)
TH
TR
Low Voltage (24 VAC)
Line Voltage (120 VAC)
LEGEND
N. C. = Normally closed switch
N. O. = Normally open switch
RO1
RO2
TYPICAL SYSTEM WIRING DIAGRAM
50A55-143
IN OTHER
FURNACES
TWINNING
APPLICATIONS
ONLY
