Forum Discussion

RatedX's avatar
RatedX
Explorer
Aug 06, 2013

Heat and A/C on at same time?

Hey guys,

Tonight I turned on my heat for the first time in a few months. Only problem was that air conditioning was running at same time. My thermostat was set to furnace NOT cool. Tried shutting it down and restarting but both where still running. Finally turned off the A/C breaker in panel to shut it down and have heat only...

Any idea what would cause this?
  • 2008Wildcat's avatar
    2008Wildcat
    Explorer
    Aug 06, 2013
    You probably have a digital thermostat, and the fan was set to auto instead of on or off.

    The new digital thermo's are set to run the fan in the a/c to help circulate the warm air. Should have just been the a/c fan running, not the compressor...
  • tanman32225's avatar
    tanman32225
    Explorer
    Aug 06, 2013
    Its funny you say that. A couple weeks ago while camping I had the AC running in the Low fan mode. We were sitting outside and I was sitting near the furnace exhaust when all of a sudden I heard the furnace running. I didnt think a thing of it at first since I had turned on the gas LP to the hot water heater. I was thinking that was what I heard. When I went inside sure enough both were running. I ended up turning everything off on the thermostat. Both AC turned off and a couple minutes later the furnace turned off. I restarted the AC and all went fine. Go figure...
  • ksbowman's avatar
    ksbowman
    Explorer II
    Aug 06, 2013
    Had the same thing happen on our home air this spring. I shut it down and restarted and all was well. Guess there was a confusion in the thermostat.
  • Clonefan's avatar
    Clonefan
    Explorer
    Aug 06, 2013
    2008Wildcat wrote:
    You probably have a digital thermostat, and the fan was set to auto instead of on or off.

    The new digital thermo's are set to run the fan in the a/c to help circulate the warm air. Should have just been the a/c fan running, not the compressor...


    This. The fan in the auto position was most likely the reason.
  • dbbls's avatar
    dbbls
    Explorer
    Aug 06, 2013
    Clonefan wrote:
    2008Wildcat wrote:
    You probably have a digital thermostat, and the fan was set to auto instead of on or off.

    The new digital thermo's are set to run the fan in the a/c to help circulate the warm air. Should have just been the a/c fan running, not the compressor...


    This. The fan in the auto position was most likely the reason.
    My fan must be in the "AUTO" to work properly. If it is on "high or low" it will run when the furnace is on.
  • Terryallan's avatar
    Terryallan
    Explorer II
    Aug 06, 2013
    dbbls wrote:
    Clonefan wrote:
    2008Wildcat wrote:
    You probably have a digital thermostat, and the fan was set to auto instead of on or off.

    The new digital thermo's are set to run the fan in the a/c to help circulate the warm air. Should have just been the a/c fan running, not the compressor...


    This. The fan in the auto position was most likely the reason.
    My fan must be in the "AUTO" to work properly. If it is on "high or low" it will run when the furnace is on.


    Mine has a fan OFF position. I put the there when the furnace is on.

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