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5
Terminal
block with
captive
screws
1
/
4
” spade terminal
1
/
4
” spade terminal
1
/
4
” spade terminal
1
/
4
” spade terminal
1
/
4
” spade terminal
1
/
4
” spade terminal
1
/
4
” spade terminal
1
/
4
” spade terminal
3
/
16
” spade terminal
1
/
4
” spade terminal
1
/
4
” receptacle
50A66
TERMINAL
TERMINAL
TYPE
SYSTEM COMPONENT
CONNECTION
TYPICAL SYSTEM WIRING TABLE
* maximum recommended flame probe wire length is 36 inches.
HLO (Pin 1)
Not Used (Pin 2)
TH (Pin 3)
Not Used (Pin 4)
RO1 (Pin 5)
TR (Pin 6)
HLI (Pin 7)
GND (Pin 8)
MV COM (Pin 9)
PSI (Pin 10)
RO2 (Pin 11)
MV (Pin 12)
IND
IGN
IND N
IGN N
W
G
R
Y
C
COOL
HEAT
PARK (3 terminals)
LINE
XFMR
EAC (optional)
HUM (optional)
120 VOLT NEUTRAL
(5 terminals)
FP (E33)
FAN
24 V HUM (E2)
low voltage thermostat W terminal (or equivalent)
low voltage thermostat G terminal (or equivalent)
low voltage thermostat R terminal (or equivalent)
low voltage thermostat Y terminal (or equivalent)
(2nd wire from Y terminal goes to 24 VAC HOT side of
compressor contactor coil)
24 VAC COMMON side of compressor contactor coil
high limit OUTPUT
24 VAC transformer (low voltage HIGH side)
rollout switch OUTPUT
24 VAC transformer (low voltage COMMON side)
high limit INPUT
MUST BE RELIABLY GROUNDED TO CHASSIS
gas valve COMMON
pressure switch INPUT
rollout switch INPUT
gas valve
inducer HOT side
ignitor HOT side
inducer NEUTRAL side
ignitor NEUTRAL side
circulator blower COOL SPEED terminal
circulator blower HEAT SPEED terminal
unused circulator blower terminals
input voltage (120 VAC) HOT side
24 VAC transformer line voltage HOT side
electronic air cleaner HOT side
humidifier HOT side
Terminals for 120 Volt NEUTRAL for line, transformer,
circulator, electronic air cleaner and humidifier
flame sensor probe*
Circulator blower fan speed terminal
24 VAC humidifier
HLO
PSO
HLI
PSI
GND
TH
TR
MV
LO
RO
OUT
RO
OUT
MV
COM
MV
IND
IGN
IND
N
IGN
N
WIRING