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Thread: Walk in freezer

  1. #1
    Join Date
    Aug 2018
    Location
    South Dakota
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    Walk in freezer

    I am working on a walk in freezer unit, trying to diagnose some issues, and need help.

    This is a big walk in with 2 exact same condensing units and evap coils. Both take turns cycling on and off.

    Box temp -3

    Watercooled condensing units
    Copeland ZF18k4-TFD liquid injected.
    R404A

    Unit A
    HP-242psi (LL- 103deg)
    LP 17psi (SL- 12deg)
    Condenser SH 30deg
    Amp draw 7.1
    Discharge temp 165

    Unit B
    HP 268psi (LL- 99deg)
    LP 17 psi (SL- 13deg)
    Condenser SH 31deg
    Amp draw 9.5
    Discharge temp 201

    Why the higher discharge temp/pressure/amp draw? Where am I getting subcooling from?
    What am I missing here?
    According to Copeland with those numbers it should only draw 7.3 amps.
    Figured liquid line restriction, changed filter, nothing changed. Both have solid liquid in sightglass with no bubbles.






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  2. #2
    Join Date
    Aug 2002
    Location
    Southold, NY
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    Is the Liquid Injection valve leaking buy?

    Sounds like unit B is weak!

  3. #3
    Join Date
    Aug 2018
    Location
    South Dakota
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    Thread Starter
    Quote Originally Posted by pecmsg View Post
    Is the Liquid Injection valve leaking buy?

    Sounds like unit B is weak!

    How would I know?
    Liquid valves are different temps.
    On unit A the liquid valve is frosty while running,
    Unit B the liquid valve is cool, but not frosty like the other one is. I did not take temps but I can.



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  4. #4
    Join Date
    Aug 2018
    Location
    South Dakota
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    Thread Starter
    Liquid injection valve on unit A is 50 degrees, unit B is 25 degrees

  5. #5
    Join Date
    Aug 2013
    Location
    Omaha
    Posts
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    "Why the higher discharge temp on unit B?"

    Well your head pressure is higher.
    You said they're water cooled, so lower the head pressure.
    Easy 1st step. I'd lower it to 240psi

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