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  1. #1
    Join Date
    Mar 2017
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    Phoenix, AZ
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    Hmm Advice on compressor short-cycling

    Hello everyone :


    I have a customer with a McQuay air cooled chiller and one of 35 HP semi-hermetic compressors is short-cycling on off cycle, sure is a leaky discharge valve, but rather then replacing the valve plate assembly. is there anything you experienced guys would recommend or do to avoid this?

    PS. You can actually hear a hissing noise like gas migrating from high to low after pump down, then system starts for 5 seconds and goes into pump-down, then starts and pumps down again. This happens over and over again.

    Was thinking of a time delay perhaps?


    Thanks all of you here.

  2. #2
    Join Date
    Sep 2002
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    Virginia
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    Thats cheating .....

    But if you wish , sure , you can install a delay timer , but they are not meant to hold much amperage , so make sure the timer runs a contactor

  3. #3
    Join Date
    Aug 2002
    Location
    Southold, NY
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    Quote Originally Posted by jlunaCR View Post
    Hello everyone :


    I have a customer with a McQuay air cooled chiller and one of 35 HP semi-hermetic compressors is short-cycling on off cycle, sure is a leaky discharge valve, but rather then replacing the valve plate assembly. is there anything you experienced guys would recommend or do to avoid this?

    PS. You can actually hear a hissing noise like gas migrating from high to low after pump down, then system starts for 5 seconds and goes into pump-down, then starts and pumps down again. This happens over and over again.

    Was thinking of a time delay perhaps?


    Thanks all of you here.
    Leaking by that badly your not doing the customer a quality service. Valve plates are cheep and fairly easy! You say 1) 35HP Semi is bad make it the lead pump!

  4. Likes trippintl0 liked this post
  5. #4
    Join Date
    Aug 2006
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    Mixing oil and fire with a big spoon.
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    Not replacing the valve plates means you will be replacing the compressor. There isn’t much lubrication going on every 5 minutes with a 5 second run time. CYA and recommend valve plates.
    "Right" is not the same as "Wise".

    Don't step on my favorite part of the Constitution just to point out your favorite part.

  6. #5
    Join Date
    Nov 2011
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    Yup, 35 is small, plates are cheap compared to a new compressor.

  7. #6
    Join Date
    Mar 2016
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    NY
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    Quote Originally Posted by 71CHOPS View Post
    Yup, 35 is small, plates are cheap compared to a new compressor.

    An ounce of prevention is worth a pound of cure!

  8. #7
    Join Date
    Oct 2011
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    Chicagoland Area
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    You're going to lose your oil.
    Officially, Down for the count

    YOU HAVE TO GET OFF YOUR ASS TO GET ON YOUR FEET

    I know enough to know, I don't know enough
    Liberalism-Ideas so good they mandate them

  9. #8
    Join Date
    Jan 2010
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    I wonder how much of that pumped out oil gets returned on a run cycle ?

  10. #9
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    Apr 2014
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    USA
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    I would personally wouldn't want my name attached to it if they don't want to make the proper repair. Make sure you keep good documentation.

  11. #10
    Join Date
    May 2003
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    Utah
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    Let's see....

    1 - Loss of capacity
    2 - High amperage
    3 - Higher discharge temperature/possible oil decomposition
    4 - Certain compressor failure down the road

    Yep...go with the time delay.

  12. Likes BALloyd liked this post
  13. #11
    Join Date
    Dec 2004
    Location
    Chicago area
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    Are you certain its the compressor valve plate?

    Could be the solenoid.


    Sent from my iPhone using Tapatalk

  14. #12
    Join Date
    Mar 2017
    Location
    Phoenix, AZ
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    Thread Starter
    Hey guys...

    Yeah, not the solenoid certainly... Tested that before getting this far for sure. We'll sometimes customers put us against the wall being freaking cheap! Any ways, ended up installing a time delay temporarily till we shutdown system for winter as we found some leaks on circuit #2 and chiller will need some major repairs on heat exchangers.

    Thanks to all of you guys for the advice.... Much appreciated !

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