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Thread: Two Bonding Jumpers. Should I get rid of one?

  1. #1

    Two Bonding Jumpers. Should I get rid of one?

    I have a situation where an old switchgear, which used to be the main service for the building, is now downstream from a new switchgear which now serves as the service entry. The new switchgear neutral and ground are bonded as required by NEC. However, the old switchgear still has a bonding jumper which bonds neutral to ground. I have asked the contractor to remove the bonding jumper in the old, downstream switchgear, but he is reluctant as he says the code does not require it.

    I've heard that having two bonds can cause ground loops, but is it also a safety issue? Is there anything in the code that forbids having bonds in two different locations?

  2. #2
    Join Date
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    Quote Originally Posted by mikeybmdb32 View Post
    i have a situation where an old switchgear, which used to be the main service for the building, is now downstream from a new switchgear which now serves as the service entry. The new switchgear neutral and ground are bonded as required by nec. However, the old switchgear still has a bonding jumper which bonds neutral to ground. I have asked the contractor to remove the bonding jumper in the old, downstream switchgear, but he is reluctant as he says the code does not require it.

    I've heard that having two bonds can cause ground loops, but is it also a safety issue? Is there anything in the code that forbids having bonds in two different locations?
    250.24(a)(5)
    Last edited by Little Bill; 02-22-11 at 10:08 PM.
    If you aim at nothing, you will hit it every time!

  3. #3
    Bill,

    Thanks a ton! I must've read that section at least twice and just glazed over that part. NEC can be so mind-numbing at times.

    -Mike

  4. #4
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    If the conductors are not the same size see 310.4.
    Advise is a dangerous gift, even from the wise to the wise.

  5. #5
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    Make sure that a separate grounding conductor was run in the feeder to the old panel. The jumper may have been left because the neutral is the only return path which of course is a violation.

  6. #6
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    The downstream bonding jumper is a safety issue, the neutral current is now in parallel with and flowing on all metal conductive paths between the two bonding jumpers. It can cause a shock or fire.
    Moderator-Washington State
    Ancora Imparo

  7. #7
    Join Date
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    Quote Originally Posted by mikeybmdb32 View Post
    Bill,

    Thanks a ton! I must've read that section at least twice and just glazed over that part. NEC can be so mind-numbing at times.

    -Mike
    Your welcome. I know, I've been numb for several months!
    If you aim at nothing, you will hit it every time!

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