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  1. #1
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    Liquid sight glass flashing



    Multi compressor rack using copeland scrolls, liquid receiver is more than half full which is 150l, but every so often I get liquid flashing through the main liquid line sight glass.
    I changed liquid distribution header with liquid exit bottom and fitted sight glasses to both liquid line.. same thing, flashing at sight glasses and receiver is half full... any suggestions??
    Last edited by irish_man; 15-07-2016 at 06:17 PM.



  2. #2
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    Brian_UK is offline Moderator I am starting to push the Mods: of RE Site Moderator : and general nice guy
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    Re: Liquid sight glass flashing

    Undersized liquid lines?
    Brian - Newton Abbot, Devon, UK
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    Re: Liquid sight glass flashing

    Quote Originally Posted by Brian_UK View Post
    Undersized liquid lines?
    All the pipe calculations done using micro calc software.

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    Re: Liquid sight glass flashing

    Is it possible that the main liquid pipe out of receiver tank is too small ? My 2 liquid stubs are 1 -3/8 & 1- 1/8, main pipe from receiver tank is only 1- 3/8..

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    Re: Liquid sight glass flashing

    What Refrigerant is it? What's the liquid temperature and pressure?

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    Re: Liquid sight glass flashing

    R507, 42 degrees liquid temp condensing pressure 280psi

  7. #7
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    Re: Liquid sight glass flashing

    You might have condensing problems from high ambient or non condensable gas in the system.

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    Re: Liquid sight glass flashing

    Quote Originally Posted by chemi-cool View Post
    You might have condensing problems from high ambient or non condensable gas in the system.
    Absolutely not, ambient here is average 35 degrees, I did triple vac and had 600 microns before adding refrigerant.

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    Re: Liquid sight glass flashing

    Hi Mate,

    I've seen something similar - in my instance was happening when the condenser fans were cycling (ON 60 seconds / OFF 60 seconds etc. operated by pressostat)

    The "falling" pressure versus to the thermal inertia of the refrigerant caused it to boil at the bottom of the swing.

    Confirmation was made by locking on a suitable number of condenser fans but locking out remainder, (no cycling = no boiling)

    Happy hunting!
    Last edited by HVACRsaurus; 17-07-2016 at 12:25 AM.

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    Re: Liquid sight glass flashing

    Quote Originally Posted by HVACRsaurus View Post
    Hi Mate,

    I've seen something similar - in my instance was happening when the condenser fans were cycling (ON 60 seconds / OFF 60 seconds etc. operated by pressostat)

    The "falling" pressure versus to the thermal inertia of the refrigerant caused it to boil at the bottom of the swing.

    Confirmation was made by locking on a suitable number of condenser fans but locking out remainder, (no cycling = no boiling)

    Happy hunting!
    Fans are controlled via electronics and minimum on/off at 5 seconds. I don't think that's the issue here. But I'll try lock on a number of fans and try your theory. Thanks

  11. #11
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    Re: Liquid sight glass flashing

    Could be just the loads/solenoids/EPR's energizing throughout the system? Momentary drop in liquid pressure and liquid lines flash. Nothing I would really worry about.

  12. #12
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    Re: Liquid sight glass flashing

    I agree with Hvacsaurus , multi fan condensers on pressure switches with minimum of 15 psi differential cause a fluctuation of liquid pressure and liquid rises and falls in liquid line. EC fans on 0-10v beautiful.

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    Re: Liquid sight glass flashing

    Hi
    I agree with Andy and HVac any type of condenser fan cycling will cause bubbles in the sight glass, also check your expansion valves superheat settings and make sure they are not "hunting" as if one or more of the TEVs are hunting this can also cause bubbles in the glass . Check and adjust them as necessary, even one with a partial loss of charge in its power assembly can cause this problem

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