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Thread: TXV Question

  1. #1
    Join Date
    Jul 2004
    Location
    NJ
    Posts
    56
    Hello guys
    This is my question
    TXV system. Refrigerant is boiling off at 25f. TXV maintaining 12f of superheat at the end of the evaporator. Since most of the evaporator is below freezing, won't it freez up?
    I was told by one of our top techs that if ( she's a sweating a TXV is ok with those temps ) Is that true?

    Doc I hope you read this
    Thank you guys

  2. #2
    Need to know the dewpoint of the entering air, it won't freeze if there is no water.

  3. #3
    Join Date
    Apr 2002
    Location
    Dallas, TX
    Posts
    2,987
    As titleless notes, entering air dewpoint would need to be known. And air velocity across the coil would prevent ice from forming on the evaporator surface if dewpoint were 25F or slightly higher.

    Off-cycle defrost is the norm for medium temp applications like this if icing becomes a problem.

  4. #4
    Join Date
    Sep 2005
    Location
    Texas
    Posts
    2,793

    use the charging

    charts that come with the equipment, you can never go wrong. Anything else is a guess

  5. #5
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,876
    Is this for a/c, or a cooler.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  6. #6
    Join Date
    Apr 2004
    Posts
    7,680
    A TXV does not control coil pressure nor does it control coil temperature. It controls superheat. No matter if you have a TXV or a piston, you will frost the coil at 25 degrees. (barring a superhigh sensible only load).

    A 25 degree coil would be suitable for a cooler and will require compressor off cycle defrost on occasion.

    Now if this were comfort cooling the problem indicates a low load which is either low airflow or a cold return. Dont look for a TXV or any other metering device to overcome a low load. You can thank your TXV, however, for protecting your compressor from being flooded.

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