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  1. #1
    rackrookie is offline Regular Member - bad email address Contact the Admin
    Join Date
    Jul 2007
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    30

    breaker tripping but not grounded semihermetic Copelamatic

    Two days ago I noticed that one of the compressors from this rack was not running. I checked the breaker and found it tripped. After resetting it, the compressor tripped it again when tried to start. Went thru the already learnt procedure of checking winding continuity and terminal to ground check. Nothing unusual. Tried to start the unit for third time, with the same breaker tripping result. Removed the oil pump and was able to turn the crankshaft by hand, so I eliminated the possibility of a mechanical lock-up. My supervisor suggested an oil check. It came out black and smelly: burnout ??? Removed the stator cover and found the winding mostly ok but with just some blackened coils. How is it possible for a stator to be burnout and still give continuity readings between the terminals and no terminal to ground path?

    By the way, any suggestion for speeding up the process of removing the old gaskets adhered to the semihermetic metal? The knife scrapping method seems to slow to me?

  2. #2
    Join Date
    Sep 2007
    Location
    Balto, MD.
    Posts
    200
    Did you check the compressor on the ohm scale, and not the continuity scale? It maybe grounded on a mega ohm scale.
    The windings are just not hitting anything going to ground. A motor can trip breakers if the windings have over heated and the resistance between the windings become too low. Usually from a section of them melting, or burning together.

  3. #3
    Join Date
    Aug 2002
    Location
    Orange County CA
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    1,084
    Quote Originally Posted by rackrookie View Post

    By the way, any suggestion for speeding up the process of removing the old gaskets adhered to the semihermetic metal? The knife scrapping method seems to slow to me?

    Yeah what he said and the gasket thing..use a ball pean hammer(spelling)
    Lightly tap directly on the gasket and it will break loose.

    Another market guy told me this...it works great.

  4. #4
    Join Date
    Feb 2004
    Location
    Medford Oregon
    Posts
    807
    using Copeland's electrical handbook, get the resistance value of the winding in ohms. if yours does't jive with the book, compressor is toast. turn to turn shorts are not shorts to ground, but will trip breaker. value should be within 5%. most bad windings are not shorts to ground but rather turn to turn shorts. you don't have to guess, just compare Ohm readings to specs.

  5. #5
    Join Date
    Jul 2000
    Location
    Guayaquil EC
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    10,076
    Quote Originally Posted by rocket View Post
    using Copeland's electrical handbook, get the resistance value of the winding in ohms. if yours does't jive with the book, compressor is toast. turn to turn shorts are not shorts to ground, but will trip breaker. value should be within 5%. most bad windings are not shorts to ground but rather turn to turn shorts. you don't have to guess, just compare Ohm readings to specs.
    Once again, rocket speaks the truth.

    Check to the spec.

  6. #6
    Join Date
    Jan 2007
    Location
    birmingham, al
    Posts
    29
    for the gasket, i use brass wire brush on drill.

  7. #7
    Did you megg out the windings yet? That will for sure verify the integrity of the windings and their condition.

  8. #8
    Join Date
    Jan 2006
    Location
    DFW Metroplex
    Posts
    4,910
    Quote Originally Posted by scott210 View Post
    for the gasket, i use brass wire brush on drill.

    Same here

    Knock off the big chunks and hit 'er with the wire wheel.

  9. #9
    Join Date
    Jun 2007
    Location
    SoCal
    Posts
    96
    Quote Originally Posted by NedFlanders View Post
    Yeah what he said and the gasket thing..use a ball pean hammer(spelling)
    Lightly tap directly on the gasket and it will break loose.

    Another market guy told me this...it works great.
    smack that gasket hard !!! its already bad !!!

  10. #10
    Join Date
    Mar 2006
    Location
    south jersey
    Posts
    454
    I use the small scotchbrite pads that go on the end of a drill just cover the cylinders with a rag first. Also the same thing rocket said check the Copeland electrical handbook for winding ohm values A good book to have on the truck also.
    Would the last person to leave NJ please put out the lights

  11. #11
    Join Date
    Aug 2002
    Location
    Orange County CA
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    1,084
    Quote Originally Posted by AngryReferGuy View Post
    smack that gasket hard !!! its already bad !!!

    You are too slow..got you again

  12. #12
    Join Date
    Jul 2007
    Posts
    4

    an old trick

    Dont use oil to apply your new gaskets. Most of us learned to soak our gaskets in oil before applying them. Years after learning this I learned sometimes its the use of oil when installing new gaskets that makes them stick.
    I always used a single edge razor blade or a sharp gasket removal tool

  13. #13
    Join Date
    Jan 2007
    Location
    maine
    Posts
    787
    i use a monster scraper.. Like what they use to scrape stickers off windshields.. works great..

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