Lennox International Inc Gas Units Heating Sequence Of Operation, Continued, Page

Troubleshooting: Heating Sequence of Operation (Continued)

HEATING SEQUENCE OF OPERATION

CONTINUED

THERMOSTAT CALLS FOR HEAT

STATUS LED − HEARTBEAT.

(Refer to box A on previous page)

FIRST−STAGE (LOW FIRE) PRESSURE	NO	GAS VALVE OFF. COMBUSTION AIR INDUCER
SWITCH CLOSED WITHIN 2.5 MINUTES?		OFF. INDOOR BLOWER OFF. UNIT WILL RETRY
YES		AFTER 5−MINUTE WAIT PERIOD.
		STATUS ERROR CODE 2 + 3.
15−SECOND COMBUSTION AIR INDUCER
PRE−PURGE INITIATED BY CLOSED FIRST−STAGE
PRESSURE SWITCH (or 15 SECOND
INTER−PURGE PERIOD.)
STATUS LED −− HEARTBEAT.

IGNITOR WARM−UP (20 SECONDS)

STATUS LED −− HEARTBEAT.

YES
			NO		COMBUSTION AIR INDUCER OFF, IGNITOR OFF.
IS IGNITOR INTACT AND CONNECTED?
					SIGNAL HOLDS UNTIL IGNITOR IS REPLACED OR
					RECONNECTED.
YES					STATUS ERROR CODE 4 + 7.
AT END OF IGNITOR 20 SECOND WARM UP
PERIOD, 4−SECOND TRIAL FOR IGNITION.
GAS VALVE OPENS, IGNITOR ENERGIZED DURING
4−SECOND TRIAL UNTIL FLAME SENSED.						YES
					IS VOLTAGE ABOVE 90 VOLTS?
YES					NO
4−SECOND FLAME STABILIZATION PERIOD.					COMBUSTION AIR INDUCER OFF, IGNITER OFF.
		NO			SIGNAL HOLDS UNTIL VOLTAGE RISES ABOVE 95
					VOLTS. STATUS ERROR CODE 4 + 8.
FLAME RECTIFICATION CURRENT CHECK
CAN FLAME BE PROVEN WITHIN 4					GAS VALVE OFF. COMBUSTION AIR
SECONDS AFTER GAS VALVE OPENS?
					INDUCER ON. INDOOR BLOWER OFF.
(u0.20 microamps)
					STATUS LED −− HEARTBEAT.
					HAS CONTROL FAILED TO SENSE	NO
					FLAME FOR FIVE CONSECUTIVE TRIES
					DURING A SINGLE HEAT DEMAND?
					YES
					WATCHGUARD MODE. GAS VALVE OFF,
					COMBUSTION AIR INDUCER OFF.	YES
					INDOOR BLOWER OFF.
					STATUS ERROR CODE 4 + 1.
					IS 60−MINUTE RESET PERIOD COMPLETE?
					YES
	NO
FLAME PRESENT?				HAS CONTROL RESET IGNITION SEQUENCE		NO
					FOUR (4) TIMES?
YES					WATCHGUARD MODE.
					STATUS ERROR CODE 4 + 3.
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