HVAC Question

(John Allingham) #1

I think this was asked a while back but I can't find it.
When testing furnaces and A/C is it OK to switch immediately from one to the other?

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(Chad Norlen, CPI) #2

You should wait a few minutes when changing from heating to cooling and vice-versa.

The biggest risk is to the compressor. There is a large pressure differential between the suction and discharge when the compressor cycles off. If it is not given time to equalize through the expansion device, the compressor won't be able to overcome that differential, and can burn a start winding, a capacitor, or bend a valve.

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(Marcel Gratton, CMI) #3

I've switched from heating to cooling without waiting for gas furnace/AC and vice versa.

Heat pumps are different.

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(John Allingham) #4

[quote="cnorlen, post:2, topic:79473"]

You should wait a few minutes when changing from heating to cooling and vice-versa.

The biggest risk is to the compressor. There is a large pressure differential between the suction and discharge when the compressor cycles off. If it is not given time to equalize through the expansion device, the compressor won't be able to overcome that differential, and can burn a start winding, a capacitor, or bend a valve.
[/QUOTE]

But I'm not talking about switching the AC off and then on again. Isn't that the situation you are referring to?

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(Chad Norlen, CPI) #5

I am. Just use caution.

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