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Thread: 250.50 and 250.52(a)

  1. #1
    Join Date
    Aug 2006
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    250.50 and 250.52(a)

    My understanding

    250.50(A) lists electrodes permitted for grounding. Assume that I selected and installed a rod electrode. Assume further that the building has a metal frame that was not relied upon to meet any of the code provisions. Further assume that the detailed methods under 250.52.(A)(2) were not complied with.

    The code talks about permitted electrodes. Thus as long as I comply with one I need not comply with any of the others.

    My assumption is that the metal frame need not be considered a grounding electrode and thus is not required to be bonded to bonded to the grounding electrode system. This is consistent with the plain meaning of the words in the code. In addition the metal frame is not part of the electrical system and is not a source of a ground fault nor is it used as a part of an effective ground-fault current path.

    A Building inspector quotes the commentary to the code
    "The Code does not specify that metal water pipe, structural metal frame, or concrete-encased-type electrodes have to be installed, only that where they have been installed as part of the building construction they are to be used as components of the grounding electrode system."

    The building inspector claims that any metal frame in a building must be bonded even if it was not used as a part of the electrical system in the building. I suspect the inspector has ignored the word permitted and finds it irrelevant that the metal frame dos not comply with the detailed provisions.

    The commentary is not code and while it may inform our understanding it cannot be the basis for a requirement not in the code.

    If I am in error explain why. Also explain why my interpretation would create an unsafe condition.

    If I am in error then I believe we will find many buildings not in compliance.

  2. #2
    Join Date
    Jul 2003
    New Jersey
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    This pretty much covers what the inspector is saying.

    250.104(C) Structural Metal. Exposed structural metal that is in-
    terconnected to form a metal building frame and is not
    intentionally grounded or bonded and is likely to become
    energized shall be bonded to the service equipment enclo-
    sure; the grounded conductor at the service; the disconnect-
    ing means for buildings or structures supplied by a feeder
    or branch circuit; the grounding electrode conductor, if of
    sufficient size; or to one or more grounding electrodes used.
    The bonding jumper(s) shall be sized in accordance with
    Table 250.66 and installed in accordance with 250.64(A),
    (B), and (E). The points of attachment of the bonding jump-
    er(s) shall be accessible unless installed in compliance with
    250.68(A), Exception No. 2.


    All responses based on the 2014 NEC unless otherwise noted

  3. #3
    Join Date
    Jan 2009
    3 Hr 2 Min from Winged Horses
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    Quote Originally Posted by infinity View Post
    This pretty much covers what the inspector is saying.
    "Electricity is really just organized lightning." George Carlin


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