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Thread: Equipment Bonding Jumper

  1. #1
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    Equipment Bonding Jumper

    I don’t understand this beast. Can someone give me an example of where it may reside?

    Here’s my problem: Consider a simple, single phase, branch circuit. I run one black wire from the breaker terminals and connect it to one side of the load. I run one white wire from the neutral bar and connect it to the other side of the load. I run one green wire from the ground bar and connect it to the case of the load. That green wire is one long wire. It does not have “two or more portions,” this phrase being taken from the article 100 definition of “bonding jumper, equipment.”

    So when does an EGC have “two or more portions”?

    This question comes from a disagreement regarding the total number of wires to be run from the secondary of a transformer (480-120/208) to the distribution panel it serves, the correct name to be given to each wire, and the correct method of sizing each wire. Let’s ignore the phase wires, and talk only about wires that have the letters “g-r-o-u-n-d” or “b-o-n-d” or that include the word “jumper.” I know it matters whether the N-G connection happens at the transformer or at the panel. In the case under discussion, it happens at the transformer.
    Charles E. Beck, P.E., Seattle
    Comments based on 2014 NEC unless otherwise noted.

  2. #2
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    Smile

    Quote Originally Posted by charlie b View Post
    . . . So when does an EGC have “two or more portions”? . .
    The following is from the 2008 Edition of the NFPA NEC Handbook. Black is the NEC and the brown is from the commentary.

    Bonding Jumper, Equipment. The connection between two or more portions of the equipment grounding conductor.

    The use of equipment bonding jumpers ensures that the electrical continuity of an effective ground-fault current path is not compromised by an interruption in mechanical continuity, as is the case with metal conduits entering an open-bottom switchboard, or an interruption of electrical continuity resulting from loosely joined metal raceways, as is inherent to an expansion fitting intended to allow for movement in a metal conduit system. Equipment bonding jumpers are used to connect the grounding terminal of a receptacle to a metal box that in turn is grounded via an equipment grounding conductor in the form of a metal raceway system. Equipment bonding jumpers around expansion fittings for rigid metal conduit as required by 250.98 are shown in Exhibit 100.4 (below). Some expansion fittings for metal conduit have an internal bonding jumper that is integral to the fitting, eliminating the need for the external bonding jumpers shown in Exhibit 100.4.

    Exhibit 100.4 Equipment bonding jumpers installed to maintain electrical continuity around conduit expansion fittings. (Courtesy of the International Association of Electrical Inspectors)

    From what I understand, the equipment bonding jumper is to connect different parts of equipment grounding conductors together as shown in the above exhibit 100.4.
    Charlie Eldridge, Indianapolis, Utility Power Guy
    Responses based on the 2011 NEC, unless stated otherwise.

  3. #3
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    Charlie b and Charlie,

    Interesting you brought this up. I have been Inspecting a new building for the Coast Guard and the EC per specs used EMT expansion Couplings across the Expansion joints in the building. They pulled an EGC in the raceway but am I missing the bond jumper? Or is this internal Bond Jumper installed in the newer expansion couplings? :confused:
    Greg

    Electrical Inspector in our Nations Capital

  4. #4
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    I would think if there is an internal EGC there would be no need for an external bonding jumper but if they wanted to use just the conduit as the EGC they would need to install a bonding jumper across the expansion joints unless they are specifically listed for grounding continuity.

    I am impressed with Charlie's picture, those expansion joints show signs of regular movement.

  5. #5
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    A lot of the newer expansion couplings are coming with an integral bonding jumper.

    Charlies picture is a good example of what the "other" Charlie is asking. A bonding jumper used around a pipe run is another example.
    Instructor, Industry Advocate

  6. #6
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    Quote Originally Posted by iwire View Post
    I would think if there is an internal EGC there would be no need for an external bonding jumper but if they wanted to use just the conduit as the EGC they would need to install a bonding jumper across the expansion joints unless they are specifically listed for grounding continuity.

    I am impressed with Charlie's picture, those expansion joints show signs of regular movement.

    There could be 2-sets of expansion couplings installed between the location where the EGC is terminated, such as at parking structures.
    Instructor, Industry Advocate

  7. #7
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    The definition of "Bonding Jumper, Equipment" in NEC 100 states:

    The connection between two or more portions of the equipment grounding conductor.

    According to NEC 250.118(2)&(3)&(4) rigid metal conduit, intermediate metal conduit and electrical metallic tubing qualify as equipment grounding conductors.
    The two or more portions would be any one of these metal raceway types that become separated either by actual breakage or by a loose fitting.
    Eric Kench, P.E.


    If it's not broken don't fix it

  8. #8
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    Quote Originally Posted by iwire View Post
    I would think if there is an internal EGC there would be no need for an external bonding jumper but if they wanted to use just the conduit as the EGC they would need to install a bonding jumper across the expansion joints unless they are specifically listed for grounding continuity.

    I am impressed with Charlie's picture, those expansion joints show signs of regular movement.
    Thanks Bob I had a brain lapse on that one for a minute. Yes EGC is installed. And yes great picture from Charlie.
    Greg

    Electrical Inspector in our Nations Capital

  9. #9
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    Charlie,
    If you make the bond to the GEC at the transformer the conductor in question would be a "system bonding jumper". 250.30(A)(1)
    If the GEC is connected at the first OCPD, then the conductor would be an "equipment bonding jumper". 250.30(A)(2)
    As far as the number of wires between the transformer and the OCPD, the same number of conductors are required no matter where you place the bonding connection. In the case where the bonding is done at the OCPD, a metallic raceway may be able to serve as the "equipment bonding jumper", but not really sure about that.
    Don, Illinois
    "It is the first responsibility of every citizen to question authority." B Franklin

  10. #10
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    Smile

    The picture is from the 2008 Edition of the NFPA NEC Handbook and is the courtesy of the International Association of Electrical Inspectors. It is not my picture, I just copied it for the post and do not want to take credit for something that is not mine.
    Charlie Eldridge, Indianapolis, Utility Power Guy
    Responses based on the 2011 NEC, unless stated otherwise.

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