47
SYSTEM TROUBLESHOOTING
NOTE: Refer to the instructions accompanying the ComfortNet compatible outdoor AC/HP unit for troubleshooting information.
Refer to the Troubleshooting Chart in the back of this manual for a listing of possible furnace error codes, possible causes and
corrective actions.
N
ORMAL
S
EQUENCE
OF
O
PERATION
POWER UP
The normal power up sequence is as follows:
• 115 VAC power applied to furnace.
• Integrated control module performs internal checks.
• Integrated control module displays 8 8 on dual 7-segment display LED’s.
• Integrated control module monitors safety circuits continuously.
• Furnace awaits call from thermostat. Dual 7-segment LED’s display O
while awaiting call from thermostat.
HEATING MODE
The normal operational sequence in heating mode is as follows:
• R and W1 (or R and W1/W2) thermostat contacts close, initiating a call for heat.
• Integrated control module performs safety circuit checks.
• Induced draft blower is energized on high speed for a 15-second prepurge. Humidifier terminal is energized with
induced draft blower.
• Induced draft blower steps to low speed following prepurge. Low stage pressure switch contacts are closed.
• Igniter warm up begins upon step to low speed and presence of closed low stage pressure switch contacts.
• Gas valve opens at end of igniter warm up period, delivering gas to burners and establishing flame.
• Integrated control module monitors flame presence. Gas valve will remain open only if flame is detected.
• If the thermostat call is for low heat, gas valve and induced draft blower will continue on low stage. If the call is for
high heat, the gas valve and induced draft blower will change to high stage.
• Circulator blower is energized on heat speed following a thirty (30) second blower on delay. The circulator blower
requires thirty seconds to ramp up to full speed. Electronic air cleaner terminal is energized with circulator blower.
• Furnace is now operating on the specified stage called for by the two-stage thermostat.
• Furnace runs, integrated control module monitors safety circuits continuously.
• If the two-stage thermostat changes the call from low heat to high heat, the integrated control module will immediately
switch the induced draft blower, gas valve, and circulator blower to their high stage settings.
• If the two-stage thermostat changes the call from high heat to low heat, the control will immediately switch the
induced draft blower and gas valve to their low stage settings. The circulator blower will remain on high heating
speed for thirty (30) seconds before switching to the low heat circulating speed.
• R and W1 (or R and W1/W2) thermostat contacts open, completing the call for heat.
• Gas valve closes, extinguishing flame.
• Induced draft blower is de-energized following a fifteen second post purge. Humidifier terminals are de-energized.
• Circulator blower continues running for the selected heat off delay period (90, 120, 150 or 180 seconds). The speed
run during this period depends on the last heat call provided by the thermostat.
If the last call for heat was a call for low heat, the air circulator motor will run on low heat speed for the duration of
the heat off delay period (90, 120, 150 or 180 seconds).
If the last call for heat was a call for high heat, the air circulating motor will run on the high heating speed for thirty
(30) seconds and then switch to the low heating speed for the balance of the heat off delay period (60, 90, 120 or
150 seconds).
• Circulator blower and electronic air cleaner terminal is de-energized.
• Circulator blower ramps down to OFF during the 30 seconds following the heat off delay period.
• Furnace awaits next call from thermostat.
COOLING MODE
The normal operational sequence in cooling mode is as follows:
• R and Y1/G or Y2/G thermostat contacts close, initiating a call for cool.
• Integrated control module performs safety circuit checks.
To Next Page
Loading...
