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  1. #1
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    Compressor short cycling....


    My father owns a bar, and one of his reach-in coolers was not working. I looked at it, and found the power wire was open. I replaced the wire, the unit came on and all was good. The next day he called and said it wasnt working agin. I looked at it and found the fans were running and the compressor would run for about 3 seconds then shut off for about 2 mins. The compressor is very hot, and the fans do not shut off.
    Any thoughts? I was at first thinking the capacitor was bad, but now thats just not making sense. Possibly lost the charge?
    The compressor is located in the basement below the cooler. It is sealed hermetic.



  2. #2
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    Re: Compressor short cycling....

    Firstly don't leave it powered up in that condition....it will take the compressor out.

    The compressor is failing to start, and cutting out on the overcurrent/temperature protector. This is probably due to the start relay and/or start capacitor (you mentioned one capacitor - value 60 - 120mfd?).
    If you have no means of testing these, then probably test by substitution. You'll need to quote the model # and make of the compressor when you source spares as relay is specific to compressor.

    The 'refrigerant charge' is not the problem at present.

  3. #3
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    Re: Compressor short cycling....

    No worry, I have the unit unplugged.
    I beleive the cap is a 60mfd, but i dont have it in front of me. I will try to swap in out in the morning, Thanks!!!

  4. #4
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    Re: Compressor short cycling....

    Is the condenser clean?

    Ian

  5. #5
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    Re: Compressor short cycling....

    Quote Originally Posted by Pooh
    Is the condenser clean?
    That would be my first question also. Look for the easy stuff first. The fans are not shutting off because the unit is calling for cooling. The problem as it sounds is because the compressor has tripped on its motor overloads/over-temperature. In this case the fans would run, while the compressor would not.

    If the compressor was hot enough to trip the over-temperature protector the condenser probably has a fur blanket on the air entering side of the condenser.
    If all else fails, ask for help.


  6. #6
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    Re: Compressor short cycling....

    Quote Originally Posted by US Iceman View Post
    That would be my first question also. Look for the easy stuff first. The fans are not shutting off because the unit is calling for cooling. The problem as it sounds is because the compressor has tripped on its motor overloads/over-temperature. In this case the fans would run, while the compressor would not.

    If the compressor was hot enough to trip the over-temperature protector the condenser probably has a fur blanket on the air entering side of the condenser.
    If "all was good" when he first started it, then the start relay and capacitor are probably okay. I also vote for the "fur blanket on the air entering side of the condenser" theory. And if that condenser is dirty, then probably every condenser in the bar is equally dirty. Time for some maintenance.
    Last edited by Gary; 21-03-2007 at 02:18 AM.

  7. #7
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    Re: Compressor short cycling....

    The day I replaced the power cord, I also did some PM, including cleaning the condenser. But thanks for the help.
    This system is old...the box is possibly from the 70's, but a fairly new compressor i think that date on the data plate was 94ish. One thing that bothered me was the power cord seemed old, maybe original. Is it possible the capacitor going caused the motor to draw to much current and the cord finally opened? I dunno HVAC is a once a month thing for me.

  8. #8
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    Re: Compressor short cycling....

    Quote Originally Posted by sbessettejr
    One thing that bothered me was the power cord seemed old, maybe original.
    Well if that's the case, the cord could have some cracked conductors in the cord. I have seen some cords where they get brittle when old. If one of the conductors has "opened up" a bit, it would act like a loose electrical connection. This forces the current to increase to "jump" the open or cracked conductor.

    Higher amperage = higher motor temperature.

    If you have an ohm meter check the cord. If not, try replacing the cord.

    The hardest part with troubleshooting a system is not finding the failed part... it's finding what caused the part to fail.
    Last edited by US Iceman; 21-03-2007 at 03:27 AM. Reason: editing
    If all else fails, ask for help.


  9. #9
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    Re: Compressor short cycling....

    Unit was only running 3 SECS!!

  10. #10
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    Re: Compressor short cycling....

    my compressore start but trip after few minute

  11. #11
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    Re: Compressor short cycling....

    my screw chiller 200TR have circuitA &B (both)start .Circuit A Trip after few minute .

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