Lennox SLP98UHV Installation Instructions Manual page 61

Troubleshooting: Heating Sequence of Operation (Continued)
RUN MODE (TWO-STAGE THERMOSTAT)
FIRST OR SECOND-STAGE CALL FOR HEAT
ALL INPUTS MONITORED (LIMIT, PRESSURE,
CALL FOR HEAT/COOL, FLAME LEVEL).
CALL FOR HEAT SATISFIED
3A
2nd Stage Heat
NO
2nd Stage
Call for Heat
satisfied?
YES
Combustion Air Inducer
switched to 70% rate speed
Adjust Indoor Blower
to appropiate speed
1st Stage Heat
NO
1st Stage
Call for Heat
satisfied?
YES
Gas valve
De-Energized
Combustion Air Inducer OFF
after 20-Second Post Purge
Indoor Blower OFF
after OFF Delay
OR
1 4
Wait for Call Wait for Call
Two-Stage Single-Stage
Thermostat Thermostat
Page 61
RUN MODE (SINGLE-STAGE THERMOSTAT)
3B
ALL INPUTS MONITORED (LIMIT, PRESSURE,
CALL FOR HEAT/COOL, FLAME LEVEL).