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Thread: Bonding in transformer and panel?

  1. #11
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    Quote Originally Posted by infinity View Post
    Ah thanks, I forgot about that one.
    I have never used it, but hope to sometime. Makes you feel like you're getting one up on the man
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  2. #12
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    [QUOTE=roger;1872603]250.30(A)(1) [I]Exception No. The transformer is 75kva so that exception would not apply, correct?

  3. #13
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    Quote Originally Posted by roger View Post
    250.30(A)(1) Exception No. 2

    Roger
    Transformer is 75kva so that exception would not apply in this instance right?

  4. #14
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    Quote Originally Posted by Ibew journeyman View Post
    Transformer is 75kva so that exception would not apply in this instance right?
    The size of the transformer doesnt matter. Generally, the only time one might use this exception is between detached structures. An application where this would be useful is where you have a long wire run where you want to step up voltage to say 480V or 600V. You would ground one of the secondary conductors and bond at both ends, thus you would only need 2 conductors for the wire run.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  5. #15
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    Quote Originally Posted by electrofelon View Post
    The size of the transformer doesnt matter. Generally, the only time one might use this exception is between detached structures. An application where this would be useful is where you have a long wire run where you want to step up voltage to say 480V or 600V. You would ground one of the secondary conductors and bond at both ends, thus you would only need 2 conductors for the wire run.
    I don't have the code in front of me but when I looked it up it had mentioned about transformer being less then 1000va for exception to be used

  6. #16
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    Quote Originally Posted by Ibew journeyman View Post
    I don't have the code in front of me but when I looked it up it had mentioned about transformer being less then 1000va for exception to be used
    Here's the exception that roger mentioned:

    250.30(A)(1)Exception No. 2: If a building or structure is supplied by a
    feeder from an outdoor transformer, a system bonding
    jumper at both the source and the first disconnecting means
    shall be permitted if doing so does not establish a parallel
    path for the grounded conductor. If a grounded conductor
    is used in this manner, it shall not be smaller than the size
    specified for the system bonding jumper but shall not be
    required to be larger than the ungrounded conductor(s).
    For the purposes of this exception, connection through the
    earth shall not be considered as providing a parallel path.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  7. #17
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    Quote Originally Posted by infinity View Post
    Here's the exception that roger mentioned:
    Thanks.. I was looking at wrong one. It says though it's permitted IF it does not establish a parallel path. How do you determine that? Do u have to test it with a multi meter? Thanks

  8. #18
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    Quote Originally Posted by Ibew journeyman View Post
    Thanks.. I was looking at wrong one. It says though it's permitted IF it does not establish a parallel path. How do you determine that? Do u have to test it with a multi meter? Thanks
    Are there any present or possible metallic paths between the panel and transformer? If there are or will be you will have multiple neutral current paths.

    Roger
    Moderator

  9. #19
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    Quote Originally Posted by roger View Post
    Are there any present or possible metallic paths between the panel and transformer? If there are or will be you will have multiple neutral current paths.

    Roger
    Just the 3 inch emt that changes over to Greenfield to carry down the conductors. That would be considered as a path for multiple neutral paths right?. I don't want to drag this out it's just I've never bonded twice, I see no reason ever to do it

  10. #20
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    Quote Originally Posted by Ibew journeyman View Post
    Just the 3 inch emt that changes over to Greenfield to carry down the conductors. That would be considered as a path for multiple neutral paths right?.
    Yes, this would be a parallel path and you are correct that it would be a violation.

    Roger
    Moderator

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