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  1. #1
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    Default Frost or ice on the outside of a heat pump compressor

    Did an inspection where both heat pumps where loaded with frost on the outside of the units. The units were running at the time. Do heat Pumps go into a defrost mode when this happens. Eventually the ice melted. One of the systems did not preform adequately. Was this the result of that. It was not that cold, in the 40s.

    Jim

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  2. #2
    Join Date
    Mar 2007
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    Default Re: Frost or ice on the outside of a heat pump compressor

    Yes, heat pumps have a defrost cycle. The frost, or ice, on the coil will stop the airflow, so it has to defrost.

    Read about Carriers heat pump defrost on page 4 of their manual.

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  3. #3
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    Default Re: Frost or ice on the outside of a heat pump compressor

    Thanks a lot Dom

    Jim


  4. #4
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    Sep 2011
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    Greater St. Louis MO
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    Default Re: Frost or ice on the outside of a heat pump compressor

    Low voltage wiring is incorrect.

    Typically, someone other than the HVAC contractor familiar with the particular brand has worked on the units.

    Did you notice if new programmable thermostadts were recently installed?


  5. #5
    Bob Cone's Avatar
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    Default Re: Frost or ice on the outside of a heat pump compressor

    The icing would be expected; todays "demand defrost" controls allow more ice to accumulate than previous control strategies. If it was that thick while you were there, then the fact that they both defrosted during your inspection is a good sign.


  6. #6
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    Mar 2008
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    Charlotte NC
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    Default Re: Frost or ice on the outside of a heat pump compressor

    Quote Originally Posted by Tom Huling View Post
    Low voltage wiring is incorrect.

    Typically, someone other than the HVAC contractor familiar with the particular brand has worked on the units.

    Did you notice if new programmable thermostadts were recently installed?
    Low voltage wiring nor thermostat are involved in the defrost cycle.

    Last edited by Vern Heiler; 12-08-2011 at 05:49 PM. Reason: double "not"
    The beatings will continue until morale has improved. mgt.

  7. #7
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    Default Re: Frost or ice on the outside of a heat pump compressor

    While we're on the subject... I've always wondered what causes the built-up on a straight A/C unit? I see it fairly infrequently (usually on the vapor line near the compressor) and write it up but don't know the cause. If I were to guess I'd think something in the system is clogged or not allowing the right flow of freon, etc.


  8. #8
    Bob Cone's Avatar
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    Default Re: Frost or ice on the outside of a heat pump compressor

    Quote Originally Posted by Matt Fellman View Post
    While we're on the subject... I've always wondered what causes the built-up on a straight A/C unit? I see it fairly infrequently (usually on the vapor line near the compressor) and write it up but don't know the cause. If I were to guess I'd think something in the system is clogged or not allowing the right flow of freon, etc.
    That is a low evaporator loading problem- not a refrigerant charge problem as is often presumed. Look for air flow restrictions and the like. Trust me, there is PLENTY of refrigerant in the system, just not enough heat (warm air) to evaporate it before it gets back to the compressor


  9. #9
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    Default Re: Frost or ice on the outside of a heat pump compressor

    Quote Originally Posted by Bob Cone View Post
    That is a low evaporator loading problem- not a refrigerant charge problem as is often presumed. Look for air flow restrictions and the like. Trust me, there is PLENTY of refrigerant in the system, just not enough heat (warm air) to evaporate it before it gets back to the compressor
    Thanks Bob.... that makes sense.


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