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  1. #1
    Join Date
    May 2005
    Posts
    1,624
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    full sight glass, still low on freon?

    Im working on a 5 glass door reach in freezer..
    temps were high in the case, its a 502 system
    I had 8/125 psi with a 30 degree box..

    i took one of the condenser fans out to get the head psi up.
    it went to 180 psi..

    anyway, i have a full sight glass, evaporator super heat is 3*

    i have the low psi control set as low as i can set it..

    compressor pumps down to 20+ inches and holds..(manually)

    any ideas??
    Let's give nukes a chance.

  2. #2
    Join Date
    Jun 2001
    Location
    Chicago Il
    Posts
    1,561
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    hmm,
    3 f superheat proves you have good charge unless your evap fans are not operating
    compressor pump down tells me the pump is good
    Can we have proper superheat with low mass flow due to bad CPR? I would say no to that.
    all data points to temp control turning off compressor when your not looking.
    low suction with warm box says CPR is closed down
    i bet compressor superheat is above 45F
    possible comp is overheating and cycling off that way.
    anyhoo, thats what i think
    If you cant fix it right, try again.

  3. #3
    Join Date
    Aug 2001
    Location
    Mechanicsville, Virginia
    Posts
    2,027
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  4. #4
    Join Date
    Dec 2006
    Location
    phoenix
    Posts
    303
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    Doesn't make sense. Minus 30 degree SST and single digit SSH with 65 degree condenser sat temp? CBR closed, frozen coil, or info isn't accurate.

  5. #5
    Join Date
    Jun 2002
    Location
    Dacula, GA
    Posts
    20,186
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    Clear sight glass with your SH, liquid line and suction pressures in the ball park means your getting the correct charge to the evaporater. Your compressor has to be shutting down. Check your controls.

  6. #6
    Join Date
    Mar 2014
    Posts
    442
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    What type of head pressure control does it use? It is possible that taking out a fan will hide a low charge from you. If it is cold out where you are and the system uses an ORI or headmaster, it's holding back too much refrigerant when the temperature drops then the txv will not be fed right

  7. #7
    Join Date
    Sep 2010
    Location
    New England
    Posts
    227
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    are you sure you have good air flow can you see through coil with flashlight. fans working and going in right direction if coil clear maybe backside of case after coil frozen

  8. #8
    Join Date
    Feb 2013
    Location
    Lamar, SC
    Posts
    834
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    They stuffing warm product in the box?
    "If you've eliminated all other possibilities whatever remains must be the truth."

  9. #9
    Join Date
    Jun 2003
    Location
    Chicago, IL
    Posts
    6,067
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    it really sounds like you have no load. is there airflow through the coil? Are you sure the plenum behind the back wall is not full of ice?

    Also are you sure the coil is actually getting cold? as in ice is visible on all the return bends? If the seals in your TXV are blown out, it will dump liquid into the suction line through the equalizer and give you a low superheat reading and possibly close the TXV depending on where the sensing bulb is in relation to the equalizer line.

  10. #10
    Join Date
    Jul 2000
    Location
    Guayaquil, EC
    Posts
    14,311
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    I agree with the no load theory. It sounds like it could be iced up.

  11. #11
    Join Date
    Jan 2010
    Location
    Sea to Sky
    Posts
    3,529
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    Case model number?

  12. #12
    Join Date
    May 2005
    Posts
    1,624
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    Thread Starter
    Ok..temp is controlled by a dual psi control..I added a psi control to the one fan i cut out of the system , it comes on at 250 psi.
    compressor is shutting off on the low side of the dual psi control, the problem is I've run out of adjustment..this thing wants to run
    into a vacuum it looks like anyway..i haven't check compressor s/h..
    evaporator is as clean as a whistle.
    Head pressure is only on the dual psi control. thats not an issue except I think its a bit low for 502..ambient is around 75/80*…No ORI or headmaster, this system is maybe 40 years old.

    no ice build up on the back side of the box.

    The TXV was a ball of ice as was the opposite end of the evap. where the copper does a 180 to go back into the coil.
    Its a tyler case, and i don't have any numbers on it, bye the compressor is a semihemetic 3.1 hp..


    thanks for all the reply guys..
    Let's give nukes a chance.

  13. #13
    Join Date
    Jul 2000
    Location
    Guayaquil, EC
    Posts
    14,311
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    Then the TXV isn't feeding...and your evaporator superheat number must be wrong.

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