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  1. #1
    Join Date
    May 2005
    Location
    North Carolina
    Posts
    38
    Just moved to NC and started servicing heat pumps. Ran into one today that is icing up ( outdoor lines and inside of the condensing unit) Checked charge when running- 150/60 What might be the cause? Could be air in ref piping system?

  2. #2
    Join Date
    Sep 2003
    Location
    Lehigh Valley, PA
    Posts
    67
    Dirty air filter and or indoor coil. Is the blower motor running? If so, is it running in the right direction. What is your superheat if fixed orifice?

  3. #3
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,347
    Air/non condensables in the circuit causing evap and suction line to ice over? Not likely. Indoor airflow problems? Very likely.

    If you're new to heat pumps, I recommend you investigate a good course of instruction for heat pumps. RSES has good material, along with other sources. The key thing to remember about heat pumps is that it is an air conditioning system that reverses itself for heating purposes. The liquid line always carries a liquid and the vapor line always carries a vapor. Both coils have metering devices and check valves but only one metering device is used pertaining to either heating or cooling mode.

    Also, many of us on the board frequently work with heat pumps so you will find a wealth of info right here.

    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  4. #4
    Join Date
    May 2005
    Location
    North Carolina
    Posts
    38
    I changed the air filter and the indoor coil looks ok- no air flow restriction. The pressures seem ok to me- other units I've serviced have worked fine at those pressures. When I originally went on the call the pressures were low and there was a leak. so I evacuated, repaired, sucked it down and charged it back up, now this. I'm perplexed. The suction line is cold and the liquid line is hot, the blower is blowing cold air but it's icing up.

  5. #5
    Join Date
    Mar 2002
    Location
    Richmond, Virginia
    Posts
    4,264
    Learn as much as you can about superheat and subcooling and a lot of your problems troubleshooting heat pumps AND straight cooling for that matter will be come much simpler. Here's a good place to start. http://hvac-talk.com/vbb/showthread.php?threadid=54493 Hit the search button above and enter superheat and continue the lesson. Everyone here is willing to help.
    There is nothing more frightful than ignorance in action....Mark Twain

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