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  1. #1
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    White Foam During Unloading



    Hi,

    I am curious to know, why liquid line sight glass start to bubble with kind of white foam during unlading of 1 bank of semi hermetic compressor.

    Compressor is 40 HP Copeland compressor. Operating conditions are 25/110F.

    Thanks in advance.



  2. #2
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    Re: White Foam During Unloading

    Sounds like liquid slugging from being overcharged or having liquid return back through the compressor.

  3. #3
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    Re: White Foam During Unloading

    Thanks BigJon,

    The foam or bubbles goes away as soon as system unloading is over.

    And the Superheat at the compressor is approx 10 deg.

    Do U still think, if this is the case of slugging?

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    Re: White Foam During Unloading

    Quote Originally Posted by jwasir View Post
    Thanks BigJon,

    The foam or bubbles goes away as soon as system unloading is over.

    And the Superheat at the compressor is approx 10 deg.

    Do U still think, if this is the case of slugging?

    What's the amp draw like during startup?

  5. #5
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    Re: White Foam During Unloading

    Quote Originally Posted by jwasir View Post
    Hi,

    I am curious to know, why liquid line sight glass start to bubble with kind of white foam during unlading of 1 bank of semi hermetic compressor.Thanks in advance.
    If it is the LIQUID LINE Sight Glass foaming,that is not an indication of slugging.
    My first thought would be that this is a because of a sudden drop of Head Pressure when the compressor unloads.
    You can verify this with your guages.
    Last edited by NH3LVR; 30-09-2007 at 06:32 AM. Reason: spelling

  6. #6
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    Re: White Foam During Unloading

    NH3LVR
    that sounds about right also the suction pressure will come up reducing the pressure differential across the metering device thus reducing flow. Without more information it is difficult to give more advice.

    Ian

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    Re: White Foam During Unloading

    This is most likely the liquid in the liquid line reaching its flash point, try increasing your subcooling so when you unload the affect is less - although I think its got to do with mass flow rates too and line sizing, I only ever see it on single systems with one liquid line, racks with headers don't tend to see this.
    ...and she said "give it to me you big fridgie"

  8. #8
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    Re: White Foam During Unloading

    Thanks to all for the nice explanation.

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    Re: White Foam During Unloading

    Quote Originally Posted by jwasir View Post
    Hi,

    I am curious to know, why liquid line sight glass start to bubble with kind of white foam during unlading of 1 bank of semi hermetic compressor.

    Compressor is 40 HP Copeland compressor. Operating conditions are 25/110F.

    Thanks in advance.
    Hi jwasir.
    What is the refrigerant R22??. Could be oil problem .
    JH

  10. #10
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    Re: White Foam During Unloading

    Quote Originally Posted by John Hunter View Post
    Hi jwasir.
    What is the refrigerant R22??. Could be oil problem .
    JH
    The Refrigerant is R-22.

    I tried to increase the sub cooling , as advised by one member.

    This didn't solved the problem completely.

    The system is complete with Low ambient package and Hot gas By-pass.

    The head pressure is maintained at 225 PSI by dumping hot gas in the receiver and also the HG by-pass is always on to maintain the min required suction pressure of 55 PSI.

    Now while charging, LL sight glass get almost clear but again starts to bubble in few minutes.

    The subcooling before the receiver is approx 30F and after the receiver is 10F.

    The comp. is 40 HP copeland with 2 unloaders. When 2 bank unloads the sight glass gets worst and less than half glass can be seen with kind of white fluid flowing in it.

    When both cylinders are loaded, the sight glass gets nice and clear.

    Does the system needs more ref. How much?

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    Re: White Foam During Unloading

    hi jwair, best way to charge your system is make sure ther is a good load on evaporator,possibly do a cuircut at a time.........also you bubbling problem sounds like you cant really help as you are dumping from the recever as you say which is liquid and by opening the by pass and exposing the high side to this pressure drop, will cause some flashing to take place...it acts like a pmv by the sounds of it

    rgrds phil

  12. #12
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    Re: White Foam During Unloading

    turn the sight glass round so u cant see it then go to the pub

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    Re: White Foam During Unloading

    Quote Originally Posted by wineman View Post
    turn the sight glass round so u cant see it then go to the pub
    I like your style
    ...and she said "give it to me you big fridgie"

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