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Thread: grounding and bonding xfmrs

  1. #11
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    Quote Originally Posted by iwire View Post
    ... But the NEC does not actually say the bonding has to be done at the point the GEC enters people assume that part.
    ...
    Here is the source of where others disagree. 250.64...

    (E) Raceways and Enclosures for Grounding Electrode Conductors

    (1) General. Ferrous metal raceways and enclosures for
    grounding electrode conductors shall be electrically continuous
    from the point of attachment to cabinets or equipment
    to the grounding electrode and shall be securely fastened
    to the ground clamp or fitting. Ferrous metal
    raceways and enclosures shall be bonded at each end of the
    raceway or enclosure to the grounding electrode or grounding
    electrode conductor. Nonferrous metal raceways and enclosures
    shall not be required to be electrically continuous.

    (2) ...
    I will have achieved my life's goal if I die with a smile on my face.

  2. #12
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    Quote Originally Posted by Smart $ View Post
    Here is the source of where others disagree. 250.64...
    Are you challenging me!





    Thank you for the code section.

  3. #13
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    Quote Originally Posted by Smart $ View Post
    Here is the source of where others disagree. 250.64...
    Here's the 2017 version which intended to clear up the confusion with some new wording:

    (E) Raceways and Enclosures for Grounding Electrode
    Conductors.
    (1) General. Ferrous metal raceways and enclosures for grounding electrode conductors shall be electrically continuous from the point of attachment to cabinets or equipment to the grounding electrode and shall be securely fastened to the ground clamp or fitting. Ferrous metal raceways and enclosures shall be bonded at each end of the raceway or enclosure to the grounding electrode or grounding electrode conductor to create an electrically parallel path. Nonferrous metal raceways and enclosures shall not be required to be electrically continuous.
    Rob

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    All responses based on the 2014 NEC unless otherwise noted

  4. #14
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    Quote Originally Posted by infinity View Post
    Here's the 2017 version which intended to clear up the confusion with some new wording:
    (E) Raceways and Enclosures for Grounding Electrode
    Conductors.
    (1) General. Ferrous metal raceways and enclosures for grounding electrode conductors shall be electrically continuous from the point of attachment to cabinets or equipment to the grounding electrode and shall be securely fastened to the ground clamp or fitting. Ferrous metal raceways and enclosures shall be bonded at each end of the raceway or enclosure to the grounding electrode or grounding electrode conductor to create an electrically parallel path. Nonferrous metal raceways and enclosures shall not be required to be electrically continuous.
    To me that new wording makes it sound like you do need a bond bushing or special clamp of some sort.
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  5. #15
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    ok, in this case it is run in pvc. the pvc does not connect directly to the xfmr case, it stops just short and the wire enters through with the mc connector.

    now with a metal raceway we would need a bond bushing to prevent impedance and 'choke points' right? that is my concern with the mc connector.

  6. #16
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    Quote Originally Posted by hacim23 View Post
    ok, in this case it is run in pvc. the pvc does not connect directly to the xfmr case, it stops just short and the wire enters through with the mc connector.

    now with a metal raceway we would need a bond bushing to prevent impedance and 'choke points' right? that is my concern with the mc connector.
    Your mc connector is a tiny raceway that is bonded to GEC because the case of the transformer is bonded. A full length metal raceway would be bonded the same way on the transformer end and would need a bonding connector of some sort on the other end.

    I don't know how much length is involved before the choke effect becomes an issue but it's a whole lot more than the length of a connector. I don't think you need the mc connector at all, but if it is there it is not going to cause any interference.
    Once in a while you get shown the light
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  7. #17
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    Quote Originally Posted by ActionDave View Post
    Your mc connector is a tiny raceway that is bonded to GEC because the case of the transformer is bonded. A full length metal raceway would be bonded the same way on the transformer end and would need a bonding connector of some sort on the other end.

    I don't know how much length is involved before the choke effect becomes an issue but it's a whole lot more than the length of a connector. I don't think you need the mc connector at all, but if it is there it is not going to cause any interference.


    To me this means that the GEC must be bonded to the ferrous raceway right at the end of the raceway, but does not necessarily need to be bonded to the transformer frame and case at that point.
    So IMO going through a mesh bottom not suitable for bonding would not be a problem as long as you used a suitable connector or clamp on the end of the raceway and then bonded the GEC to the transformer metal at or near the X0 terminal.

    Not in the code AFAIK, but one could argue that there could be a choke effect (very small) just from going through the wall of a ferrous metal enclosure. If that turned out to be a legitimate concern, then you would have to bond the incoming raceway to the case and the case to the X0 in addition to running the GEC to the X0.

  8. #18
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    Quote Originally Posted by GoldDigger View Post
    ...
    Not in the code AFAIK, but one could argue that there could be a choke effect (very small) just from going through the wall of a ferrous metal enclosure. If that turned out to be a legitimate concern, then you would have to bond the incoming raceway to the case and the case to the X0 in addition to running the GEC to the X0.
    In the op's case there is no incoming raceway. Just a pvc sleeve which terminates prior to the GEC penetrating the transformer enclosure.
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  9. #19
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    Quote Originally Posted by GoldDigger View Post

    To me this means that the GEC must be bonded to the ferrous raceway right at the end of the raceway, but does not necessarily need to be bonded to the transformer frame and case at that point.
    So IMO going through a mesh bottom not suitable for bonding would not be a problem as long as you used a suitable connector or clamp on the end of the raceway and then bonded the GEC to the transformer metal at or near the X0 terminal.

    Not in the code AFAIK, but one could argue that there could be a choke effect (very small) just from going through the wall of a ferrous metal enclosure. If that turned out to be a legitimate concern, then you would have to bond the incoming raceway to the case and the case to the X0 in addition to running the GEC to the X0.
    Are there suitable connectors listed for single conductors?
    Rob

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    All responses based on the 2014 NEC unless otherwise noted

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