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  1. #1
    Join Date
    Jul 2006
    Location
    West Plains, Missouri, United States
    Posts
    82

    Confused Low Superheat Low subcooling

    Hey fellas. I was working on a 10 year old trane heatpump today. TXV R-22 system. Filters good. Vents open. Compressor was replaced last October (According to owner).
    16 Degree delta T @ Gas Furnace. Upflow unit.
    Suction Pressure was 80, 5 degrees superheat.
    Liquid line pressure was 208 @ 4.5 degrees subcooling. 90 degree ODT
    Makes a loud thump when unit turns on after just a second or so. Suspect thats the reversing valve.
    I am wondering if the reversing valve is by-passing hot liquid into the low side of the system. So far it is all I can think of that would lower the superheat while raising the suction pressure and lower the head pressure and subcooling.

    Thoughts? Suggestions?
    Thanks in advance.

  2. #2
    Join Date
    Aug 2013
    Posts
    111
    TXV Bulb is loose or poorly insulated? Higher amps to the compressor?

  3. #3
    Join Date
    Sep 2010
    Location
    Indiana
    Posts
    336
    What was indoor temperature and wet bulb?

  4. #4
    Join Date
    Jul 2009
    Location
    Columbia, MD
    Posts
    3,789
    Check valve could be bypassing a little in Txv. A leaky reversing valve would give you higher sh and higher discharge sh. Is Txv adjustable?

  5. #5
    Join Date
    Apr 2013
    Location
    Independence, MO
    Posts
    135
    5 degree superheat would indicate a flooding evaporator for a TXV system which would raise suction pressure due to lack of restriction. Was target evaporator temp spot on or low based on return dry bulb and return wet bulb? Was condensor clean ?
    Advice is always free, but keep in mind free does not mean it's always right.

  6. #6
    Join Date
    Jul 2006
    Location
    West Plains, Missouri, United States
    Posts
    82
    hi JKerch.
    I dont have all my readings with me. I will need to check and get back with you.

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