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Old 05-15-2016, 06:40 PM   #1
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Heat pump question


My question is about the outdoor unit, and when it should run...

In AC mode, the fan on the outdoor unit cycles on and off with the indoor unit (more or less).

In Heat pump mode, the outdoor unit seems to be "short-cycling." not sure if that is the correct term, but it will turn on, run for about 30 seconds, then shut off...The indoor unit continues to run throughout this process...

Any advice would be appreciated--is this normal?

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Old 05-15-2016, 07:29 PM   #2
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Re: Heat pump question


That is not normal, and could be causing harm to the unit by running that way. Sounds like a pressure switch opening and closing.

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Old 05-15-2016, 07:55 PM   #3
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Re: Heat pump question


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Originally Posted by roughneck View Post
That is not normal, and could be causing harm to the unit by running that way. Sounds like a pressure switch opening and closing.
I did have an issue earlier this spring--after turning on the heat pump after it being off all winter (I have oil for the cold months)...I had a repair company out--they stated I had no pressure and recharged the system completely (9lbs). Also put is a dye to see where it was leaking. They came back two weeks later--the system pressures tested perfect, and they could not find any leaks using the UV light.

System has been off for a few weeks, and now this problem...

Why would it run fine (not short cycling) AC side, but cycle on and off on the heat side?
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Old 05-15-2016, 08:21 PM   #4
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Re: Heat pump question


If the system was out of refrigerant and no leak was found, then it's probably low again. Refrigerant isn't a consumable material, so your system doesn't just need to be recharged from time to time.
Different amounts of refrigerant can be needed between heating and cooling. Various refrigeration side problems can show up in one mode and not the other.
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Old 05-15-2016, 08:31 PM   #5
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Re: Heat pump question


I do know that refrigerant tis not a consumable, so i clearly must have a leak...but if the pressure is indeed too low, why would the Heat side cycle on and off (seems to me it should stay off)...Also, why would it keep running without issue on the AC side?
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Old 05-15-2016, 09:18 PM   #6
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Re: Heat pump question


Suction pressure drops when the system runs, then equalizes when the system is off. So that will produce the cycles you describe.
Exactly why yours is doing it will have to be checked to see.
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Old 05-15-2016, 10:20 PM   #7
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Re: Heat pump question


Outdoor would be colder then inside air. So when running in heat mode, your suction often will be lower then when in cooling mode. (pressure in this case is related to temperature)

It is typical to have problems in one mode before seeing problems in the other mode as refrigerant slowly leaks out.

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Old 05-16-2016, 07:14 AM   #8
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Re: Heat pump question


Could be a bad TEV. Heat pump will usually have one for indoor coil, one for outdoor coil....and they each have a reverse flow check valve (internal or external). System can run properly in one mode...but not the other.

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