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Thread: Grounding bushing?

  1. #1
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    Grounding bushing?

    Just got a correction notice on a building that we wired. The correction notice says that we need to install "grounding bushings" on a branch circuit. Basically out of a 480v panel, there is a branch circuit that runs to a closet where a disconnect is mounted. Out of the disconnect it feeds a plenum heater. The reason for the correction is cause we used concentric knockouts for the pipe. We also have our egc ran in the pipe. Am I missing a code section which requires me to have bonding bushings, on a 480v branch circuit, using concentric knockouts, while also having an egc installed with the circuit conductors?
    I realize that if I didn't have an egc in the pipe while using the concentric, it would justify using bonding bushings. Any clarification would be appreciated.

  2. #2
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    The Code Section would be 250.97 which would be applicable as far as the raceway being bonded regardless of the presence of an actual conductor.
    There are some exceptions referencing the listing of enclosures but they might well not apply in your situation.
    At my age, I'm accustomed to restaurants asking me to pay in advance, but now my bank has started sending me their calendar one month at a time.

  3. #3
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    In general disconnect switches with concentric or eccentric KO's are not listed as suitable for bonding.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  4. #4
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    Awesome. Thanks. That clears things up.

  5. #5
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    Quote Originally Posted by Dr Duke View Post
    Awesome. Thanks. That clears things up.
    Just to clarify I was referring to over 250 volts to ground {250.97} in my previous post.
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  6. #6
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    Quote Originally Posted by Dr Duke View Post
    Awesome. Thanks. That clears things up.
    In some cases a bonding wedge or split collar bushing can save time when you've forgot to use a bonding bushing.

  7. #7
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    Quote Originally Posted by Electricalartist View Post
    In some cases a bonding wedge or split collar bushing can save time when you've forgot to use a bonding bushing.
    Yes those split bushings can be a life saver when someone forgets about 250.97. Can a bonding wedge be used with concentric KO's?
    Rob

    Moderator

    All responses based on the 2014 NEC unless otherwise noted

  8. #8
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    Quote Originally Posted by infinity View Post
    Yes those split bushings can be a life saver when someone forgets about 250.97. Can a bonding wedge be used with concentric KO's?
    Yes as long as it's used with a bonding jumper

  9. #9
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    Quote Originally Posted by infinity View Post
    In general disconnect switches with concentric or eccentric KO's are not listed as suitable for bonding.
    Do you know any examples of equipment with ring KO's that are listed for 277V or 277/480V bonding? I'd like to see how this is noted on a datasheet. I understand that these will be a lot more heavy duty than ordinary knockouts, and more difficult to remove.

  10. #10
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    Quote Originally Posted by Carultch View Post
    Do you know any examples of equipment with ring KO's that are listed for 277V or 277/480V bonding? I'd like to see how this is noted on a datasheet. I understand that these will be a lot more heavy duty than ordinary knockouts, and more difficult to remove.
    Some 4S boxes are, you can tell has the KOs are hard to remove. I have a picture in my grounding class of an approved box but not sure if I have any on the shelf
    Moderator-Washington State
    Ancora Imparo

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