I am just noticing this running the heat. If I set the thermostat to 70 it will run and run and the temperature reads 70 but the unit does not shut off. If I turn it up to 72 and then when it reaches 72 bump the setting down to 70 it will shut off. It is super cold here for Florida but I don't remember noticing this with the AC on.

I have had my unit serviced in the summer and had the pistons cleaned out and haven't had any issues since. Thanks AB

  • How long have you seen it run? Does the air coming from the registers get cooler after the set temp is reached? It's normal for a heating system to turn off the heat but keep the blower running for a minute or so to cool off the hot components.
    – JPhi1618
    Commented Jan 18, 2018 at 16:07
  • It is running hours as far as I know. It doesn't appear to get hotter in the house though so I am confused.
    – user80536
    Commented Jan 18, 2018 at 16:14
  • Is this a heat pump? Do you have Auxiliary/Emergency heat (electric or gas)?
    – JPhi1618
    Commented Jan 18, 2018 at 16:22
  • It is electric. Yes I have noticed the Aux heat keeps kicking on as well. But it was 28 here this morning. It goes back and forth between the aux and heat. My unit is only 3 years old thou but not sure about thermostat. Thanks for any help you can provide. Because it is never this cold I am hoping its for that reason only but I would think it would shut off. I know the AC had been shutting off.
    – user80536
    Commented Jan 18, 2018 at 16:27
  • I do see some frost on my coils it is just got over freezing here so not sure if I should remove it. I do we have a slow freon leak as well we were told in the summer.
    – user80536
    Commented Jan 18, 2018 at 16:41

1 Answer 1


This may not be the answer, but here's what I make of it...

Heat pumps have a maximum temperature they can reach when it's cold outside. It sounds like for you, this temp might be around 70 degrees.

What my heat pump thermostat will do is call for heat when the temperature drops more than one degree lower than the set temp. So, if I have it set to 70, the heat pump kicks on at 68.5. If the temp falls another degree or two (mine is adjustable), it realized that the heat pump can't do it on its own, so it calls for aux heat. It normally won't turn off until the temp is above the set temp, so it would run until the house got to 71 (again, this is adjustable).

What may be happening is that your aux heat is turning on when your thermostat falls to 68, but then it turns off when it reaches 70, but the heat pump stays on trying to get the house up to 71. That never happens - the temp actually falls back to 68 and the aux heat comes on and the process repeats.

If your thermostat has adjustable points at where aux heat comes on and when it shuts off after reaching the desired temp, you could adjust those so it does turn off. The other option is to just switch to "Emergency heat" when its very cold outside. The heat pump won't operate and all heat will come from Aux heat. This isn't normally what you want to do, but in extremes, it could be needed. Right now my house in Texas is on Emerg heat because it was 15 degrees last night.

  • That may be it because it was 28 here and the house could not get warm. I notice when we have a fire we don't have this issue. I never noticed this happening before either so could just be the cold. I will keep an eye on it
    – user80536
    Commented Jan 18, 2018 at 16:47
  • I feel like the thermostat should keep the aux heat on until the the house is warm enough for the system to turn off completely, but I'm not sure if that's the case on any or all thermostats. I haven't paid that close attention to mine - I just switch to emergency heat when it's that cold.
    – JPhi1618
    Commented Jan 18, 2018 at 16:49

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