Short Cycling

[rwand1]

Thanks John thats good info.

Have come across a few induced draft blowers that sound like water is being retained in the bottom of the fan housing. One in particular would short cycle, while the other did not. Both were high efficiency models.

In those cases I put in the report - service furnace prior to closing of title.

Thanks
Raymond Wand
Alton, ON

[jrupert]

When I hear that it is normally a drain issue with the pvc rather then a clogged secondary heat exchanger ( I have only had one of those in 20 years), and the condensate from combustion backs up and you get that water sound in the inducer blower

[JLilly]

Like say your results may vary.

[Dean Call]

Sorry Raymond, when you said "safety shut-down" I wasn't thinking about the pressure switch that proves flue draft.
However I've never seen a pressure switch that would cause "short cycling" but I suppose it's possible. I have seen many that kept the burners off though for various reasons.

The manual reset vent safety switches/back draft switches are normally in or near some part of the flue system and detect flue draft problems VIA high temperatures. They could also be just a rollout switch since a flue not drawing will cause burner "rollout" depending on the type of furnace

A heat anticipator on an electronic digital thermostat is not something you can physicallysee, it's adjusted by certain procedures called out in the installation instructions. (as in press/hold this button and that button to adjust heat cycles, press/hold this button and that bitton to adjust cooling cycles.)

Just speaking in general terms since there are so many different brands with their own individual characteristics.

[rwand1]

Thanks for the info.

Regards
Raymond Wand
Alton, ON

[phinsperger]

Originally Posted by twheeler

I would like to throw this question out there.
What causes short cycling in a gas forced air furnace?

Originally Posted by twheeler

The Most Common cause of short cycling, is "failure of the thermostst".

This must be the Tyrone Wheeler QOD

[Robert R. Foster]

My 90% gas furnace is short cycling too. Stat calls for heat, induced draft blower comes on, burner ignites and in about a second and a half burner shuts down. I have a programmable stat with no antisapater ajustment. ???