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Thread: Would like some input please

  1. #1
    Join Date
    Nov 2015
    Location
    Ellington, CT
    Posts
    23

    Would like some input please

    I currently have an 8 floor apartment building. There are two three phase 120/208 owners panels that feed common areas with a common basement. The building was built and wired in 1963. I have a 1 inch rigid pipe run in the slab that goes directly from the panel to a 12 x 12 box in a utility closet. The conduit has 8 Branch circuits and three neutrals. I have a situation where phases A and C will trip when both of them are turned on. They work independently of each other. They feed LED stairwell lights and a Fob entry system. On a continuity check they do not ring phase to phase or phase to ground or phase to neutral. Because of the ampacity, at one point someone put three circuits on A phase and 3 circuits on C phase. I split each circuit and put it on its own breaker. I still have what appears to be a phase to phase short no matter how I split them up. Even if I take the circuit from A phase and put them on C phase and vice versa still trips. I have since put them on C phase in the tap box on a spare circuit​ coming from the panel. as they only draw 1.3 amps combined and haven't had any problems yet. Would anyone have any idea what in the world is going on?
    Any and all help would be greatly appreciated.

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  2. #2
    Join Date
    Jul 2005
    Location
    Tennessee
    Posts
    15,326
    What happens if you disconnect all the associate loads and the j box and simply energize both branch circuits to the j box ?
    At my age, I'm accustomed to restaurants asking me to pay in advance, but now my bank has started sending me their calendar one month at a time.

  3. #3
    Join Date
    Nov 2015
    Location
    Ellington, CT
    Posts
    23
    They trip...... but still don't show continuity phase to phase, phase to neutral, phase to ground

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  4. #4
    Join Date
    Dec 2006
    Location
    Chapel Hill, NC
    Posts
    31,991
    I would turn off all breakers and disconnect all loads at the jb and see what you get. You will always get a short reading if you read thru a circuit that has a load connected. If you still have a short then you have a short in the wire

  5. #5
    Join Date
    Nov 2015
    Location
    Ellington, CT
    Posts
    23
    I did try that, put a meter on it and don't have continuity. Put it back together and still trips. I am completely baffled by this issue. In 27 years I have yet to come across this problem

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  6. #6
    Join Date
    Jul 2015
    Location
    Wilmington, NC USA
    Posts
    239
    I'm confused about which breakers are tripping.

  7. #7
    Join Date
    Dec 2007
    Location
    NE Nebraska
    Posts
    32,475
    Megohmeter might be your friend on this one.

  8. #8
    Join Date
    Nov 2015
    Location
    Ellington, CT
    Posts
    23
    A phase and C phase. Even if I move to B phase, it still trips. It trips before the j box but doesn't come up any where else before that. I used different meters to check for continuity and still nothing.

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  9. #9
    Join Date
    Nov 2015
    Location
    Ellington, CT
    Posts
    23
    I didn't think of megging it...... what's your train of thought? A break down somewhere in the conductor in the conduit too slight to ring but enough to trip?

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  10. #10
    Join Date
    Jul 2015
    Location
    Wilmington, NC USA
    Posts
    239
    Quote Originally Posted by bsmith8691 View Post
    A phase and C phase. Even if I move to B phase, it still trips. It trips before the j box but doesn't come up any where else before that. I used different meters to check for continuity and still nothing.

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    What trips, all breakers, the main breaker? How many breakers on each phase, one for each circuit (8)? Is it only 1 breaker tripping? Which breaker?

    Remember, we have not seen and do not know what you are looking at, so EVERY detail needs to be communicated by you to us if you are to receive good help.

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