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Troubleshooting: Heating Sequence of Operation (Continued)
WHEN USED WITH A SINGLE STAGE THERMOSTAT, SET SW1 TO THE ON POSITION IN DIP SWITCH S4.
IF THE HIGH FIRE PRESSURE SWITCH DOES NOT CLOSE WITHIN 5 ATTEMPTS, THE SYSTEM WILL OPERATE AT
LOW FIRE FOR THE REMAINDER OF THE CALL FOR HEAT REQUEST.
2ND STAGE GAS VALVE
ENERGIZED
ONLY FOR 1ST
REQUEST FOR
2ND STAGE HEAT
YES
CALL FOR HEAT SATISFIED
INDUCER SWITCHED
TO HIGH SPEED
SINGLE STAGE
THERMOSTAT
2 STAGE THERMOSTAT
NO
INDUCER SWITCHED
TO LOW SPEED
5 MINUTE DELAY
(ERROR CODE FLASHES)
HIGH
PRESSURE SWITCH
CLOSED WITHIN 10
SECONDS?
2ND STAGE
ON DELAY
EXPIRED?
CALL FOR 2ND STAGE HEAT
(HIGH FIRE)
2
3
1
2
3
1
2
3
YES
YES
CALL FOR SECOND−STAGE HEAT
RECOGNITION DELAY
(30 SECONDS)
EXPIRED?
INDOOR BLOWER ENERGIZED
ON HIGH HEAT SPEED
SYSTEM WILL ALWAYS LIGHT ON LOW FIIRE, EVEN IF 2ND STAGE HEAT IS IN PLACE.