Does this harm the unit?

[Dub Smith]

It is 100+ degrees in Oklahoma right now and, of course, every home has the A/C running. During the HVAC inspection, is there risk to switch from Cooling to Heat to check the unit? I know you can't check the A/C if it is 65 degrees or cooler outside, but is there such a limitation on the heating unit? What steps do some of you take to switch between the two?:)

Sorry, I just noticed I posted in the Plumbing Forum and not the HVAC.... oops!

[George Hallaron]

Dub,

To the best of my knowledge there is no harm in switching from A/C to heat other than, the discomfort felt in the house during the operation of the heating unit. when it's 100+ deg. outside, I can't imagine the current homeowner being too thrilled about the idea of having to pay to re-cool the house after the heater has been heating up the walls & such. This is not my specific area of expertise, however it has never caused a problem for me down in the gulf south.

[Jimmy Roberts]

No matter where you are geographically located, there is no harm is cycling a thermostat from cooling, to heating, whether testing or otherwise. During a test, the heating function would be operating for less than a minute, so there is not going to be a detectable energy loss. Even if there was a detectable energy loss to recool, the testing process is required to confirm operational function.

[Garry Sorrells]

My best knowledge is that switching from heating to cooling will have no negative effect on system. Similar to a temporary loss of power. If the AC unit was switched on and off in quick succession the compressor may shut down for 1 to 2 min then it would restart.

[Nick Ostrowski]

What type of heating system are you talking about?. Up here in PA, I don't run a heat pump in heat mode if it is 60 degrees or hotter but I will test the emergency backup mode. If it's a gas or oil-fired heating system, I'll run it regardless of temperature.

[Dub Smith]

Thanks everyone for your replies. I was at an inspection this morning and I had a realtor call me down and said that her Heating and Air guy has always told her to have the A/C turned off at least an hour before turning on the heat. I had never heard this and was wondering if I was screwing up. So Nick, what are you saying, run the emergency heat mode only? How is this different from the Heat mode itself? Thanks for your help!:)