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Grounding two feeders in a separate building and bonding process piping

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    Grounding two feeders in a separate building and bonding process piping

    Hi.
    Here's the scenario- doing some significant renovations on a small separate building. Of course no existing plans/drawings. The building has two three phase feeds (<600V) to separate panels, each with its own EGC. We are relocating one panel and adding breakers to both.

    Part 1- Per NEC 250.32, we need to add a grounding electrode system. A grounding rod will probably be easiest. Then we can tie the ground rod to the EGC at panel 1. Can we also tie panel 2 to the same ground rod? I believe the NEC allows this second connection (250.30(6)), but I haven't run into this scenario before. I'll also bond to the building steel to ensure it's grounded. How long ago did this requirement for a GES at a separate building enter the Code? Many electricians seem not to know about it.

    Part 2- there is a lot of metal process piping in the building- cold water, steam, etc. It should all be bonded per NEC 250.104 in case it accidentally becomes energized.

    Thanks for any insight.

    Jay

    #2
    In general, 225.30 limits you to a single feed to a second building.

    The grounding electrode system must be installed and connected to the EGC at the second building

    The requirement for a grounding electrode system at a second building has been in the code for many years. It was required by 250-24(a) in the 1978 code, the oldest one I have around.

    Prior to the 2008 code, you could use the grounded conductor as both the grounded and grounding conductor to the second building, with restrictions. Starting with the 2008 code, you are required to run both a grounded and grounding conductor from the first building.
    Don, Illinois
    (All code citations are 2017 unless otherwise noted)

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      #3
      Thanks for the response. Yea I'm working on the 225.30 issue too, but think I'll meet it.

      If the two feeders remain, they can share the same GES, right?

      Wow, surprised it goes back to 1978. Wonder why there's so much confusion about it.

      Thoughts regarding the metallic mechanical piping?

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        #4
        I don't see any issue using the same grounding electrode conductor.

        Bonding piping is only necessary if it is likely to be energized. Basically if the piping is isolated from any electrical then you would not necessarily have to bond it. 250.104(B). The question is argued as to what constitutes likely to be bonded really means
        They say I shot a man named Gray and took his wife to Italy
        She inherited a million bucks and when she died it came to me
        I can't help it if I'm lucky

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          #5
          I'm finding that sources online say to ground gas/metal piping:
          http://www.ecmag.com/section/codes-s...ing-gas-piping
          http://www.csstfacts.org/protecting-gas-piping.aspx

          Even though to me it doesn't seem like they are likely to become energized. But I guess with a near electrical strike you could have a voltage difference which would cause problems. Anyone have experience with their AHJ or otherwise about what 'likely to become energized' means and if they ground gas, steam, or similar piping?

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