Lennox EL280UH110P60C Unit Information page 33

Troubleshooting: Heating Sequence of Operation (Continued)
CONTINUED
SECOND−STAGE (HIGH FIRE) HEAT
PRESSURE SWITCH CLOSED?
YES
HEAT DEMAND SATISFIED?
STATUS LED −− HEARTBEAT.
YES
SINGLE−STAGE THERMOSTAT MODE
(DIP SWITCH SET AT SINGLE")
YES
GAS VALVE OFF, COMBUSTION AIR
INDUCER OFF AFTER 5−SECOND
LOW SPEED POST PURGE PERIOD,
INDOOR BLOWER OFF DELAY
INITIATED ON LOW HEAT SPEED.
STATUS LED −− HEARTBEAT.
DEMAND FOR HEAT SATISFIED.
POWER ON STAND BY.
STATUS LED −− PULSE.
HEATING SEQUENCE OF OPERATION
NO
YES
TWO STAGE THERMOSTAT MODE?
(DIP SWITCH SET AT TWO")
YES
FIRST AND SECOND STAGE HEAT
YES
DEMAND SATISFIED SIMULTANEOUSLY.
STATUS LED −− HEARTBEAT.
Page 33
SEE BOX A
NORMAL OPERATION.
SEE BOX B
THERMOSTAT CALLS FOR HEAT.
RETURN TO FIRST−STAGE HEAT MODE.
FIRST−STAGE CONTINUES UNTIL SECOND−
STAGE PRESSURE SWITCH CAN BE PROVEN
or HEAT DEMAND IS SATISFIED. A FIVE (5)
MINUTE WAIT PERIOD IS INITIATED BEFORE
RETRY. WERE 5 ATTEMPTS MADE FOR
SECOND−STAGE HEAT?
NO
SEE BOX C
FIRST−STAGE HEAT DEMAND SATISFIED?
NO
STATUS LED −− HEARTBEAT.
GAS VALVE, COMBUSTION AIR INDUCER
AND INDOOR BLOWER RETURN TO FIRST−
STAGE OPERATION.
STATUS LED −− HEARTBEAT.
FIRST STAGE HEAT DEMAND SATISFIED?
YES
GAS VALVE OFF. COMBUSTION AIR INDUCER
OFF AFTER 5−SECOND LOW SPEED POST−
PURGE PERIOD. INDOOR BLOWER OFF.
DELAY INITIATED ON LOW HEAT SPEED.
STATUS LED −− PULSE.
YES
SECOND STAGE HEAT
DEMAND SATISFIED?
YES