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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).
508364-01
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
1
4
OR
Wait for Call
Wait for Call
Two-Stage
Single-Stage
Thermostat
Thermostat
Issue 2346
RUN MODE (SINGLE-STAGE THERMOSTAT)
3B
ALL INPUTS MONITORED (LIMIT, PRESSURE,
CALL FOR HEAT/COOL, FLAME LEVEL).
Page 69 of 74
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