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Thread: Bonding conduit

  1. #1
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    Waxahachie tx USA
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    Bonding conduit

    I am wanting to know if I need to bond my 3/4 inch conduit.

    The only wire in it is a 1/0 ground. There are no current carrying conductors in the conduit.
    It is the grounding system for a 400 amp service in a commercial building.

    The purpose of the conduit is to protect the ground wire from abuse as it is in an unsecured area subject to potential vandalism.

  2. #2
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    If the conduit containing the GEC is ferrous metal then yes you must bond the conduit to the GEC.

    See 250.64(E) for the fine details

    When you run a single isolated conductor in a ferrous conduit and then apply a strong current to the conductor as would happen during a fault the combination of the single conductor and ferrous conduit raises the imdeance of the circuit.

    By bonding the conduit to the GEC at each end you make the conduit and conductor act as a single conductor.

  3. #3
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    Quote Originally Posted by iwire View Post
    If the conduit containing the GEC is ferrous metal then yes you must bond the conduit to the GEC.

    See 250.64(E) for the fine details

    When you run a single isolated conductor in a ferrous conduit and then apply a strong current to the conductor as would happen during a fault the combination of the single conductor and ferrous conduit raises the imdeance of the circuit.

    By bonding the conduit to the GEC at each end you make the conduit and conductor act as a single conductor.

    What if it is metallic conduit, but non-ferrous, like aluminum conduit?

  4. #4
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    Quote Originally Posted by Carultch View Post
    What if it is metallic conduit, but non-ferrous, like aluminum conduit?
    Non-ferrous metal raceways are not required to made continuous....and does not require the same connections.
    *All code responses are based on the 2017 National Electrical Code[NEC]

  5. #5
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    Bonding the Al conduit would lower the impedance, due to lightning is high frequency and tends to travel on the skin of the conductor. Information on why we bond metallic conduits for a GEC is in the IEE Green Book
    Moderator-Washington State
    Ancora Imparo

  6. #6
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    Quote Originally Posted by tom baker View Post
    Bonding the Al conduit would lower the impedance, due to lightning is high frequency and tends to travel on the skin of the conductor. Information on why we bond metallic conduits for a GEC is in the IEE Green Book
    Doing and Requiring are two different beasts.....
    *All code responses are based on the 2017 National Electrical Code[NEC]

  7. #7
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    Nj
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    Any conduit installed,when conductive, must have a means to trip the breaker if a current carrying conductor comes in contact with it. Emt will remain energized in the event of a fault unless bonded

  8. #8
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    Quote Originally Posted by Electricalartist View Post
    Any conduit installed,when conductive, must have a means to trip the breaker if a current carrying conductor comes in contact with it. Emt will remain energized in the event of a fault unless bonded
    However in most cases just a standard connector and lock nut do that job.


    In the case of an EGC are required to do more bonding than that.

  9. #9
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    Quote Originally Posted by iwire View Post
    In the case of a [GEC] you are required to do more bonding than that.
    Corrected

  10. #10
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    Quote Originally Posted by Carultch View Post
    Corrected

    Thank you.

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