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Thread: Ungrounded Panelboard

  1. #1

    Ungrounded Panelboard

    We are working in a plant where we have found several 120/208 VAC 3-phase, 4-wire panelboards that are ungrounded (no ground conductor or ground bus). Should we at a minimum have an electrician bond the panel(s) to the building ground grid or leave it as is?

  2. #2
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    Is there a metallic conduit feeding the panel? If is it may be fine as is.
    Rob

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    All responses based on the 2014 NEC unless otherwise noted

  3. #3
    Yes, The Panel(s) are fed with Rigid Metal Conduit (RMC) and all loads from the panel are also run in RMC.

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    Quote Originally Posted by dcheser View Post
    Yes, The Panel(s) are fed with Rigid Metal Conduit (RMC) and all loads from the panel are also run in RMC.
    If so, it already has an equipment grounding conductor as RMC is allowed to be used as an EGC.
    Bob

  5. #5
    Quote Originally Posted by petersonra View Post
    If so, it already has an equipment grounding conductor as RMC is allowed to be used as an EGC.
    Is there anything in the code that we can reference with respect to this?

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    Quote Originally Posted by dcheser View Post
    Is there anything in the code that we can reference with respect to this?
    250.118 lists equipment grounding conductors and RMC is on the list so there is no code issue with your installation.
    Rob

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    All responses based on the 2014 NEC unless otherwise noted

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    Quote Originally Posted by dcheser View Post
    Is there anything in the code that we can reference with respect to this?
    As well as being code approved it is also worth noting that RMC is a better equipment ground than any copper wire you could stuff in it.
    Once in a while you get shown the light
    In the strangest of places if you look at it right. Robert Hunter

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    Quote Originally Posted by ActionDave View Post
    As well as being code approved it is also worth noting that RMC is a better equipment ground than any copper wire you could stuff in it.
    FWIU, during a fault with rmc/emt with a wire type egc pulled, the bonded pipe will actually carry more of the fault current than the wire. All that extra conductive surface makes a great low r path.

  9. #9
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    Are bond bushings required when using a conduit as the EGC? I have not been able to find any requirements in the NEC.

  10. #10
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    Quote Originally Posted by alan232 View Post
    Are bond bushings required when using a conduit as the EGC? I have not been able to find any requirements in the NEC.

    With regards to your question in the OP no not required.


    Is the voltage over 250 volts to ground? If yes then maybe, if no then probably not required with a possible exception.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

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