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Trailer Chassis Grounding

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    Trailer Chassis Grounding

    We have 6 office trailers joined as one office space. Each trailer have a separate panel and separately fed from a Distribution panel with 6 circuits.

    Each panel is bonded and grounded to its own ground rod.

    Is there a requirement to bond the chassis of each trailer to the ground rods?

    Thank you

    #2
    just out of curiosity, what article of the code covers trailers being used as offices?

    I don't recall there is any special requirements for such trailers so unless the chassis of the trailer somehow qualifies as a grounding electrode, or is likely to become energized, I don't see the code requires bonding. As a practical matter, it may already be bonded in some way.
    Bob

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      #3
      Originally posted by rl2 View Post
      We have 6 office trailers joined as one office space. Each trailer have a separate panel and separately fed from a Distribution panel with 6 circuits.

      Each panel is bonded and grounded to its own ground rod.

      Is there a requirement to bond the chassis of each trailer to the ground rods?

      Thank you
      My take is this kind of joined office trailer arrangement is a single 'manufactured building' per 545.2. That is if I can walk from one to the other without going outside, its one building. If not then treat each one as a separate structure.
      Is the main distribution panel you refer to located on the office space? In that case create a grounding electrode system there with at least two of the groundrods bonded to the ECG bar. That MDP then feeds the sub panels in each trailer wing of the common building.
      If the MDP is not on the office space and there are 6 feeders to one building it gets tricky.
      Unless they meet one of the exceptions under 225.30 I doubt you can have 6 feeders to a single building.
      If you can then I think you still need to group all the disconnects in one location (225.34) and create a common GEC bonding point there as described in 250.64(D), then feed the sub panels from there.
      Back to your original question 545.11 requires you to provide for the bonding and grounding, of all exposed metals likely to become energized, in accordance with Article 250. So yeah verify a #6 to the sub frame from each sub panel, often this is already done at the factory.
      The remaining four ground rods are just extras and will fall under 250.54 if its not easy to tie them into a common GEC.
      Cheers
      Comments based on 2017 NEC unless otherwise noted.

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