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  1. #1

    Contactor single phasing after 4 days

    Working on a ref plus remote unit for a coffin/bunker freezer, the system will burn the contactor lags out within 4 days causing it to single phase and go off on oil failure. I am having trouble as to why the contactor lags are burning out cause i am having proper voltage across all three phases, proper amperage, no bleeding through the contactor, it does not chatter, i have an auxilary switch on it so that the defrost and compressor never run at the same time and i have made sure that the contactor is properly sized. Any ideas?

  2. #2
    Join Date
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  3. #3
    Join Date
    Dec 2008
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    Quote Originally Posted by jpsmith1cm View Post
    Are you SURE????

    I mean REALLY, REALLY, SURE?
    Ditto-something must be causing chatter to burn it out this soon.

  4. #4
    I am watched it for probably 5 hours turning it on and off, cycling it through defrosts and pumping it down can not find a way to make it chatter, every time i show up it is running properly once the contactor is changed

  5. #5
    Join Date
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    Location
    Gold Coast of Connecticut
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    Time delay

    Quote Originally Posted by darcy.welch3 View Post
    I am watched it for probably 5 hours turning it on and off, cycling it through defrosts and pumping it down can not find a way to make it chatter, every time i show up it is running properly once the contactor is changed

    ICM Delay on make, set for 5 seconds or more.
    Aire Serv of SW Connecticut- Gas heat, dual fuel and central a/c systems installed and serviced

  6. #6
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    Quote Originally Posted by Freezeking2000 View Post
    ICM Delay on make, set for 5 seconds or more.
    Not a bad idea.

    Only other thing is contactor sizing?

    Is the contactor big enough for the load?

  7. #7
    Join Date
    Jul 2001
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    Gold Coast of Connecticut
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    I assumed the contactor was rated properly....what is the contactor rating?

    Is it possible the compressor is flooding back and locking up? Do you have superheat numbers?
    Aire Serv of SW Connecticut- Gas heat, dual fuel and central a/c systems installed and serviced

  8. #8
    Superheat is 15 degrees at the compressor and 8-10 at each txv, there is 6 txv in the bunker, the contactor is 40 FLA and 50 Res the max circuit of the unit is 25amps

  9. #9
    Join Date
    Apr 2010
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    working overtime
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    Take amp draw on condenser fan motor. Maybe it's failing periodically and causing chattering off hp switch.

  10. #10
    Join Date
    Nov 2006
    Location
    Southeastern Pa
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    18,812
    I would check every contact in the coil circuit of the contactor, too.

  11. #11
    Okay thanks everyone for the input

  12. #12
    Join Date
    Jul 2011
    Location
    Lehigh Valley, PA
    Posts
    464
    Assuming the cables & contactor are both sized for the amp capacity, check you cable ends. Are your cable ends burnt up? Did you cut them back exposing clean copper? Is the control voltage solid? This and what others have already stated.

  13. #13
    Join Date
    Apr 2010
    Location
    San Diego, CA
    Posts
    226
    I recently saw a head pressure switch that was intermittently causing contactor chatter. Seems like it's gotta be something like that.

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