White Rodgers 50A55-438 Typical System Wiring Table, Terminal, System Component, Connection, Type

TYPICAL SYSTEM WIRING TABLE

50A55	TERMINAL	SYSTEM COMPONENT
TERMINAL	TYPE	CONNECTION
W		low voltage thermostat W terminal (or equivalent)
G	Terminal	low voltage thermostat G terminal (or equivalent)
R	block with	low voltage thermostat R terminal (or equivalent)
Y	captive	low voltage thermostat Y terminal (or equivalent)
	screws	(2nd wire from Y terminal goes to 24 VAC HOT side of
		compressor contactor coil)
C		24 VAC COMMON side of compressor contactor coil
MV (2 terminals)		gas valve (both gas solenoids are connected in parallel)
TR		24 VAC transformer (low voltage COMMON side)
TH		24 VAC transformer (low voltage HIGH side)
FP	12-pin	flame sensor probe*
PS	connector	pressure switch INPUT
HLI	& harness	high limit INPUT
HLO		high limit OUTPUT
GND		MUST BE RELIABLY GROUNDED TO CHASSIS
(3 unused terminals)
IND		inducer HOT side
IGN	4-pin	ignitor HOT side
IND N	connector	inducer NEUTRAL side
	& harness
IGN N		ignitor NEUTRAL side
COOL	spade terminal	circulator blower COOL SPEED terminal
HEAT	spade terminal	circulator blower HEAT SPEED terminal
PARK (2 terminals)	spade terminal	unused circulator blower terminals
LINE	spade terminal	input voltage (120 VAC) HOT side
XFMR	spade terminal	24 VAC transformer line voltage HOT side
HUM (optional)	spade terminal	humidifier HOT side
EAC (optional)	spade terminal	electronic air cleaner HOT side
CIR N	spade terminal	circulator blower NEUTRAL terminal
LINE N	spade terminal	input voltage (120 VAC) NEUTRAL side
XFMR N	spade terminal	24 VAC transformer line voltage NEUTRAL side
HUM N (optional)	spade terminal	humidifier NEUTRAL side
EAC N (optional)	spade terminal	electronic air cleaner NEUTRAL side

* maximum recommended flame probe wire length is 36 inches.

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