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Thread: Generator Frame and GEC

  1. #1
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    Generator Frame and GEC

    Is the frame of a generator set up as an SDS required to have it's own GEC run to the building GES? The generator frame has 4 switches mounted directly to it with bonded neutrals and each with a separate GEC run to the GES.
    Rob

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    All responses based on the 2014 NEC unless otherwise noted

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    Quote Originally Posted by infinity View Post
    Is the frame of a generator set up as an SDS required to have it's own GEC run to the building GES? The generator frame has 4 switches mounted directly to it with bonded neutrals and each with a separate GEC run to the GES.
    We've had this question come up a number of times. I'm assuming you have the typical outdoor genset that many would say is a separate structure and thus not require the 2 GES be bonded together. I not sure the code directly addresses this but I will say that it is a pretty common situation since we rarely see gensets inside the structure it is serving anymore. I'm inclined to say that the 2 GES should be bonded together.

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    I see no reason to run a GEC between the generator and the building, but an EGC, or in some cases a supply side bonding jumper will be required between the two locations and that will bond the two grounding electrode systems together.
    Don, Illinois
    (All code citations are 2017 unless otherwise noted)

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    I should have mentioned this is a generator within a room in the building. There is a large lug on the frame that says "ground", we're being told to run a GEC to that lug I was just wondering why it's needed. Could it simply be due to manufacutrer's instructions?
    Rob

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    All responses based on the 2014 NEC unless otherwise noted

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    I don't see anything in 445 other than 445.20(A)(B)

    As an aside , we recently mitigated a few gfci ocpd's tripping on transfere , by simply lifting the genset bond 'floating' the noodle.

    ~RJ~

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    The lug "ground" requirement is done by the manufacturer, they typically don't have an understanding of the NEC. Mike Holt went round and round with Generac over this issue. Our AHJs required a connection to the lug under 110.3(B).
    Moderator-Washington State
    Ancora Imparo

  7. #7
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    Quote Originally Posted by infinity View Post
    I should have mentioned this is a generator within a room in the building. There is a large lug on the frame that says "ground", we're being told to run a GEC to that lug I was just wondering why it's needed. Could it simply be due to manufacutrer's instructions?
    Given that it is in the same building and connected as a SDS then its GES would need to connected to the building GES and with your experience I'm sure you get that. I think being a SDS that "ground" lug becomes moot.

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