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  1. #1
    Join Date
    Sep 2009
    Posts
    22

    True Reach in Cooler

    I have a question about a unit I was working on.

    I responded to a call about a unit that was making a smooshing noise every 5 min or so while the unit was running. I get there and first thought was internal relief valve. I throw some guages on...

    Low side 45 psi (10 degrees)
    High side 330 psi (125 degrees).
    Cap tube with subcooling of 50 degrees?? Liquid line was 75 degrees.

    Every time the swooshing noise starts the High side opens the relief at 330 psi it and closes at about 250ish.

    The part I dont understand. There is a suction dryer installed. The first time I took temp split across the drier I had 14 degrees differance. I assumed this would cause a restriction and make refrigerant back up in the condensor. A few minutes later I checked again and it was only a 1.5 degree diff across the suction dryer.

    This is where I am stuck. Any thoughts?

  2. #2
    Join Date
    Oct 2009
    Posts
    28
    What kind of refrigerant?

  3. #3
    Join Date
    Jun 2003
    Location
    Chicago, IL
    Posts
    4,344
    There was probably liquid refrigerant sitting in the evap, which got sucked out and collected in the suction line dryer when the comp started. As this liquid evaporated it created the temp drop you saw.

  4. #4
    Join Date
    Sep 2009
    Posts
    22
    Quote Originally Posted by invisiblecollar View Post
    What kind of refrigerant?
    Unit is 404a

  5. #5
    Join Date
    Sep 2009
    Posts
    22
    Quote Originally Posted by craig1 View Post
    There was probably liquid refrigerant sitting in the evap, which got sucked out and collected in the suction line dryer when the comp started. As this liquid evaporated it created the temp drop you saw.
    If that is true then I am really at a loss of what this could be..

  6. #6
    Join Date
    Jun 2003
    Location
    Chicago, IL
    Posts
    4,344
    is the condenser clean?

  7. #7
    Join Date
    Sep 2009
    Posts
    22
    Quote Originally Posted by craig1 View Post
    is the condenser clean?
    Yes the condensor is clean.

  8. #8
    Join Date
    May 2010
    Location
    Trenton, Mo
    Posts
    47
    Without hands on this is only a guess but should be checked. POE oil breaks down under high condensing temperatures to a very fine powder that will go through driers, screens and cap tubes, causing partial restrictions. It will also coat the inside of the condenser and evaporator. If you find this fine black/gray powder in the system, that is the problem. The fix is to flush the system and replace the cap tube or tubes. Also don't forget to replace any driers and the cap tube strainer. Last of all, be aware that the problem could have caused damage to the compressor. This could become an expensive fix. I hate/love POE oil.
    Last edited by DDDpope; 05-02-2010 at 10:53 PM. Reason: compressure damage

  9. #9
    Join Date
    Jan 2010
    Posts
    6,088
    Is that a suction dryer or a suction accumulator ?

  10. #10
    Join Date
    Apr 2010
    Location
    San Diego, CA
    Posts
    197
    Sure it's a cooler and not a freezer? I haven't seen a True cooler that had 404a in it, usually they're charged with 134a.

    More often than not a restriction in the system doesn't cause high head pressure unless it's before the condenser, in the compressor discharge line. Look for the obvious, of course. Kinked copper or whatever. Some of those things have steel discharge lines, someone may have got a little bit crazy with the 56% silver brazing in a new compressor and partially filled the discharge line.

    Condenser fan spinning the right way? IIRC those things use the little shaded pole motors you can pick up at any supply house, someone may have put the wrong one in.

  11. #11
    Join Date
    Sep 2009
    Posts
    22
    Quote Originally Posted by VTP99 View Post
    Is that a suction dryer or a suction accumulator ?
    Suction Dryer

  12. #12
    Join Date
    Sep 2009
    Posts
    22
    Quote Originally Posted by cmclifton View Post
    Sure it's a cooler and not a freezer? I haven't seen a True cooler that had 404a in it, usually they're charged with 134a.

    More often than not a restriction in the system doesn't cause high head pressure unless it's before the condenser, in the compressor discharge line. Look for the obvious, of course. Kinked copper or whatever. Some of those things have steel discharge lines, someone may have got a little bit crazy with the 56% silver brazing in a new compressor and partially filled the discharge line.

    Condenser fan spinning the right way? IIRC those things use the little shaded pole motors you can pick up at any supply house, someone may have put the wrong one in.

    I mispoke and it is a McCall Freezer/Refrigerator according to name plate.

    As far as kinks and bends I did not see any. No frosting on liquid line.

    Fan is going the right way.

  13. #13
    Join Date
    Jul 2000
    Location
    Guayaquil EC
    Posts
    10,264
    Quote Originally Posted by The_chief View Post
    I mispoke and it is a McCall Freezer/Refrigerator according to name plate.

    As far as kinks and bends I did not see any. No frosting on liquid line.

    Fan is going the right way.
    A refrigerator/freezer is a horse of a different color.

    If it's a single compressor model, that whooshing you describe may be from a liquid solenoid valve to the refrigerator section cycling on and off. If that's the case you appear to be overcharged when running only on the freezer section.

    If you do have a restricted cap tube, the system may have been overcharged to get the suction pressure up...resulting in the high head pressure and high subcooling.

    If you do replace the cap tube, it's imperative that you also change the compressor oil. If you don't, you'll be back fairly soon because the crap that plugged it up is still lurking in that dirty oil.

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