Run A/C in winter on heat pump

Don’t run into many heat pumps in the area of the country that I work and was wondering if the air conditioning side of a heat pump should be tested in the winter. Is there any potential damage that could be done by testing the A/C when the temperature is under 35 degrees?

From the classes I have taken, it has always been recommended that you do not use a heat pump in AC mode if the temperature is below 65 degrees F.

Up here in the north I do not run any A/C equipment if it has been below 60 in a 24 hour period prior to the inspection.

What about a forced air system with a condenser?

same thing

It’s my understanding that you don’t run it when the temp is under 65.

I have also been told that if the heat side works, then you can safely assume that the cold will also.

I could be wrong, about this, but I think it just runs in reverse to cool. So that being the case everything should be fine if heat mode works.

Also be sure to test the emergency heat mode as well. (That works more like an electric furnace.)

This is a heat pump not an air conditioner (there is a difference). If you don’t know what the difference is, then keep away from it.

This is another example of inaccurate information taught in home inspection school.

A heat pump operates in the air-conditioning mode about 20 times a day! It is designed to run in the air-conditioning mode in the winter. It has all kinds of stuff in it to keep it from breaking like an air conditioner would.

If you know what it is you’re testing, it’s perfectly acceptable to run in the air-conditioning mode. It is not going to operate and give you a 20° dT (which is another old wives tale from HI school) in the wintertime because there is no heat load for the equipment to operate under design conditions.

The only way for a home inspector to test the reversing valve is by turning on the air-conditioning. If you don’t test reversing valve’s than don’t test the air-conditioning mode.

The air-conditioning components operate in both heating and cooling, so if it’s working in the heat mode it will work in the cooling mode if the reversing valve is operational.

Test procedure: turn up the heat, grab a hold of the big refrigerant line and it should be hot. Go look at the electric meter and see if it’s spinning like a top (electric heaters are working). Switch over to the air-conditioning mode and the big refrigerant line should cool off if the reversing valve operated.

You’re done!

Maybe a little too simplified for a “test procedure”.
Heres some more info for those that need it.

Some systems have programmed lockouts to keep the heat strips off unless its below a programmed set point outside…

The refrigerant line does not get hot immediately…

Many electric meters do not have any moving parts to observe during electric heat mode…

Many systems have a 5 minute delay when switching from heat to cool or vice versa…

If it is 35, and you turn on the AC, how cold do you expect it to be at the registers??? :wink:

Don’t turn it on. :smiley:

I often turn on the AC condenser briefly just to verify that it will activate. I say this for air conditioners:

“We did not test the air-conditioning system thoroughly because the ambient temperature is too low, and testing it could damage the coil. However, we turned it on for less than 1 minute to verify that the condenser(s) would activate.”

I say this for heat pumps (no need to turn it to AC mode):

“The heat pump(s) responded to a request for heat in normal mode, but was not tested on the cooling cycle because the ambient temperature is too low and to do so could damage the coil. But generally speaking, if the unit works in the heat mode, it should work in the A/C mode.”

Activation is not proper operation

If there were to be a problem because of low ambient temps it would be immediately upon activation of unit. If there was a problem and one were to let it continue to run for a minute you just bought a condensing unit. Do some research of the major manufacturers some allow AC operation in low temp conditions down low as 40 °F. Most of the newer units allow operation well below the 65 °F mark.


Only if the reversing valve is working properly


Sure, I know that. I was speaking generally. You are speaking specifically. I may modify my statement to say “…provided the reversing valve is functional.” That would be better.

Don’t run the heat pump in air conditioning mode in winter, it’s pointless and you are proving nothing. The only observation you can make when doing so is that the reversing valve is operational and even that observation is limited.
You can make the same limited observation that the reversing valve is operational by noting that there is no ice on the outdoor section which would indicate that the defrost cycle is operational and therefore the reversing valve.
Even though the reversing valve operates you can’t make any assumptions that the heat pump will operate satisfactory in air conditioning mode without proper heat loads and operating conditions. Mark it down as a limitation to the inspection due to low ambient conditions. I have seen heat pumps that appear to work satisfactory in heat mode but perform unsatisfactory in the air conditioning mode.
Observations about heat pumps and air conditioners are very limited when it comes to home inspections due to the amount of information required to properly diagnose
the equipment operation and the procedures and tools for collecting this information.
Stick to the basics and operate heat pumps and air conditioners as they are designed to be operated under the correct ambient conditions.
Although everyone knows what you mean when you say condenser coil and evap coil, Heat pump coils are more properly referred to as indoor coil and outdoor coil. This is because the reversing valve determines which is the condenser coil (heat rejecting) and which is the evaporator coil (heat absorbing).

Yup, that has been covered to death here!
Don’t go there, it is not well accepted.
Also, don’t make it so easy (as above) as that is not accepted either. :-k