Furnace Cycling Too Often

Old 12-02-11, 07:29 PM
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Furnace Cycling Too Often

I have an old Carrier 58GSC that seems to be cycling too often. The sequence is something like the following:

1. Heat is called for by the stat.
2. Igniter fires and lights the pilot.
3. Pilot burns for approx. 1 min.
4. Main burner fires up and burns for another 1 min.
5. Blower comes on, with main burner staying lit, and runs for 2-3 min.
6. Pilot and main burner turn off, fan keeps running for approx. 2 min.
7. Igniter fires, lights the pilot, and the cycle repeats.

This doesn't seem right to me. Shouldn't the main burner stay lit with the fan running for a longer period of time? Any troubleshooting help would be greatly appreciated.

Old 12-03-11, 03:21 AM
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check for air restrictions.... filter, evap coil, all registers open.

Could also be a faulty limit
could also be a bad heat exchanger
Old 12-03-11, 09:11 AM
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HVAC Tech is suggesting that the furnace may be overheating and shutting off on the high temperature limit switch -- and that certainly worth checking.

I'd also be concerned that the thermostat itself is cycling too often. Use a voltmeter to determine if the limit switch is opening, or whether power is being interrupted top the "W" terminal on the furnace, which would indicate that the thermostat is shutting the furnace off.

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