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  1. #1
    Join Date
    Feb 2005
    Posts
    281
    can this be true? new 2 door reach in 35 deg.cooler,r134a,capillary tube feed,mistakenly overcharged, after 1-1/2 weeks went back to find evap. coil,suction line froze up. i thought if overcharged, evap. coil could not ice up. any thoughts?

  2. #2
    Welcome Joe.
    Here's a recent thread which covers your question.
    It has 128 replies.

    http://hvac-talk.com/vbb/showthread.php?threadid=73668

    Now if that is not enough .... well I dont know what to say.


    But you've certainly come to the right place.


    We are the Premier mechanics of the industry here. We happen to like what Don did when he started this site.


    We just added the information.


    (Beware of Dice)...... (and do not answer any questions about goats.)

    [Edited by R12rules on 05-07-2005 at 03:54 PM]

  3. #3
    Join Date
    Feb 2005
    Posts
    281
    where is the thread?

  4. #4
    Join Date
    Apr 2005
    Location
    AZ
    Posts
    191
    http://hvac-talk.com/vbb/showthread.php?threadid=73668
    I think this is the thread he meant

  5. #5
    Join Date
    Sep 2001
    Location
    East Stroudsburg, PA
    Posts
    13,215
    Originally posted by mud
    http://hvac-talk.com/vbb/showthread.php?threadid=73668
    I think this is the thread he meant
    10 pages on an iced evap. Wow. That'll keep ya busy for awhile.

  6. #6
    Join Date
    Feb 2005
    Posts
    281
    thanks guys,after reading 10 pages i think i will keep my opion to myself

  7. #7
    Originally posted by joebear
    thanks guys,after reading 10 pages i think i will keep my opion to myself

    Joe, freely share your opinion here. After all ... if DiceMan can share his ... why shouldnt you share yours?

    Who knows ..... maybe the two of you can balance this forum out?!?!?!....



  8. #8
    Join Date
    Mar 2005
    Location
    Alberta, Canada
    Posts
    474
    Joebear Print this off and stick it into your wallet. Will help you along find the right path


    if not than follow this handy flow chart

  9. #9
    Join Date
    Oct 2004
    Posts
    3,400
    Originally posted by joebear
    can this be true? new 2 door reach in 35 deg.cooler,r134a,capillary tube feed,mistakenly overcharged, after 1-1/2 weeks went back to find evap. coil,suction line froze up. i thought if overcharged, evap. coil could not ice up. any thoughts?
    We know an overcharge can and will raise the temperature of the evaporator.

    However, that WILL cause it to freeze up, in this application.

    Consider the defrost cycle.

    A 35 degree cabinet normally runs the evaporator somewhere around ten to fifteen degrees, well below the freezing point of water.

    Many of these coolers use a constant-cut-in thermostat to control defrost (random off-cycle). Maybe 37 degrees.

    The bulb of this type of thermostat is in contact with the evaporator coil, not suspended in the air.

    That means the coil must reach a fixed, predetermined temperature before calling (close-on-rise).

    The cut out, is usually adjustable, but will be somewhere around 15 degrees, typically, for medium temp.

    If the unit is supposed to shut off when the coil reaches a setpoint of fifteen degrees, but an overcharged condition has the coil running at twenty-five, then the compressor will just continue to run. Heat load from the product will keep it from going cold enough to cycle.

    It can't shut off, hence no defrost.

    Therefore, a medium-temp coil CAN ice up due to overcharge.

    Mind bogglin', ain't it?



  10. #10
    Join Date
    Apr 2005
    Location
    Australia : Queensland
    Posts
    797
    Joebear. 1st year apprentice here has it got a accumulator on the return side to the compressor after the evap if not it will need a critical charge.

  11. #11
    Join Date
    Aug 2002
    Location
    manitowoc wisconsin
    Posts
    4,943
    I like the flowchart bryan
    Take your time & do it right!

  12. #12
    Join Date
    Nov 2003
    Location
    Stamford CT
    Posts
    33
    Originally posted by joebear
    can this be true? new 2 door reach in 35 deg.cooler,r134a,capillary tube feed,mistakenly overcharged, after 1-1/2 weeks went back to find evap. coil,suction line froze up. i thought if overcharged, evap. coil could not ice up. any thoughts?
    Is it a coil sensing thermostat? An overchargeg cap tube system will run a higher suction pressure. It is very possible that the suction pressure/evaporating pressure is not low enough to satisfy the thermostat, but is under freezing. Leading to your freeze up.

  13. #13
    Join Date
    Dec 2002
    Posts
    603
    I don’t believe that an over charge is the cause of the evap and suction line froze up, its more likely a an inefficient evaporator,like a dirty coil, a fan running too slow, recirculated air, or product interferance. However, according to the mollier diagram on a cap tube system with a gross overcharge, pressures will increase (but not equally) while suction and discharge gas temperatures decrease, sub-cooling will increase, (thereby decreasing the bubble length) suction specific volume will decrease and the COP will be slightly increased. So it may be possible that the evap and suction can freeze up(but not likely) if a cap tube system is overcharged, it will back up the excess liquid into the condenser, causing high head pressures. The pressure difference between the low and high sides of the system will now increase, increasing the refrigerant flow rate to the evaporator and overfeeding the evaporator, causing low superheats. It may even flood or slug the compressor. So was the compressor still operable and the oil not washed out? I think a better choice of refrigerant is HC12a-a hydrocarbon. It will blend with all refrigerant oils-mineral or synthetic. We have replaced all R134a units with this refrigerant in our shop class's with very good results

    [Edited by shogun8 on 05-23-2005 at 10:11 AM]

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