Thread: Heat Pumps

Why is it not a good idea to inspect a heat pump in the heat mode during hot weather and in the cool mode during cold weather?

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ive never had an issue of doing that, its only the reversing valve you are testing, test as normal, below 40 deg. in the heat mode is not very effetive

I've always heard that running a heat pump in the cool mode during cold weather could damage the compressor because of the lubricant in the compressor, which I suppose is not warm and not very lubricating. However, I also understand that it is not good to run a heat pump in the heat mode during warm weather; I don't understand why?

Since the heat pump picks up heat from the outside air, on a hot day the refrigerant pressures can get too high and cause damage. Most likely it won't be it could. It is okay for a HVAC tech to run the system because he can monitor the pressures with his gauges.

Originally Posted by Timothy Crotts

I've always heard that running a heat pump in the cool mode during cold weather could damage the compressor because of the lubricant in the compressor, which I suppose is not warm and not very lubricating. However, I also understand that it is not good to run a heat pump in the heat mode during warm weather; I don't understand why?

The heat pump runs in the cooling mode every time it automatically runs a defrost cycle. You can't hurt it by running "cooling mode" in cold weather.

Originally Posted by mike huntzinger

ive never had an issue of doing that, its only the reversing valve you are testing, test as normal, below 40 deg. in the heat mode is not very effetive

Below 40 deg? You must be talking about the old heat pumps.

The new ones that use R410 work really good down to about 26 degrees.
They still work below that but need an occasional boost from the electric strips.

I have tested both of mine with the electric strips programmed to stay off to see how they did in really cold weather. This was done on a well insulated house with high end windows and R38 in the attic.

Originally Posted by Timothy Crotts

I've always heard that running a heat pump in the cool mode during cold weather could damage the compressor because of the lubricant in the compressor, which I suppose is not warm and not very lubricating. However, I also understand that it is not good to run a heat pump in the heat mode during warm weather; I don't understand why?

As the others have said, heat pumps are okay... you might be thinking about an air-conditioner. Those shouldn't be run below 65 for the reasons you cite.