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  1. #1
    Join Date
    Oct 2013
    Location
    wilmington nc
    Posts
    2

    hvac tech,since 1980,trying to get the hang of things

    looking for the topic of restriction vs low charge,have some questions on this subject

  2. #2
    Join Date
    Oct 2013
    Location
    wilmington nc
    Posts
    2
    i have a restriction on a 3 toh heat pump,had a nother tech thinks it is a low charge,i hace a unit that has 2 floaters,one at the cap tubes,the outher is about 10 inch back of the cap,the first one 10 inch back is frosting up fron there and starts freezeing up into to the evap,what do you think,this schoud be a easy one

  3. #3
    Join Date
    Feb 2006
    Location
    Austin, Texas
    Posts
    355
    add a little refrigerant if the superheat does not change its a restriction. If the charge was low the superheat would go down.

  4. #4
    Join Date
    Jun 2012
    Location
    Fayetteville, NC
    Posts
    312
    Quote Originally Posted by zviking View Post
    back is frosting up fron there and starts freezeing up into to the evap[/B],what do you think,this schoud be a easy one
    If you are referring to the indoor coil as the evap coil, then I would suspect a restriction.

  5. #5
    Join Date
    Aug 2013
    Location
    Visalia California 93291
    Posts
    1,332
    High sub cooling high super heat =restriction

  6. #6
    Join Date
    Jan 2005
    Location
    southeast
    Posts
    83
    I agree with Ikapigian Subcooling is the only way !

  7. #7
    Join Date
    Feb 2004
    Location
    New Mexico
    Posts
    5,720
    Actually if you just grab the liquid line and feel the temp. A low charge will be passing hot gas along with liquid and be hotter than expected. A restriction will be colder than expected. Adding charge isn't a good first approach. Actually even putting on the gauges is somewhat down the line.
    "What Fools these mortals be"....Puck

  8. #8
    Join Date
    Jan 2005
    Location
    southeast
    Posts
    83
    You can't have hot gas and liquid in the line together. If it was saturated meaning there is no subcooling, vapor and liquid would be in the line at the condensing temperature. Low charge would drop the head pressure reducing saturation temperature and line temperature. A restriction would back up the liquid in the condenser increasing subcooling and reducing line temperature. Without knowing the saturation temperature in the condenser you would just be throwing darts at guessing whats wrong without checking the suction for low or high superheat. I do agree that a small loss of charge could reduce the subcooling in the condenser raising the liquid line temperature but only if small enough not to drop the head pressure.

  9. #9
    Join Date
    Feb 2006
    Location
    Austin, Texas
    Posts
    355
    Just put a little gas in it. If the suction pressure changes you will know what to do. Suction goes up, short of gas, no change, restricted. Quick and easy. Hell, you don't even need to check superheat, subcooling. Ya don't even have to know what superheat, subcooling, saturated is. Most a/c guys don't! It's not complicated.

    dick

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