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Thread: PV system grounding, EGC vs GEC, irreversible splices

  1. #1
    Join Date
    Jul 2014
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    Washington DC
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    PV system grounding, EGC vs GEC, irreversible splices

    Hello,
    I believe that GEC's often require irreversible splices, but as far as I can tell in many cases the ground from a solar PV racking system (module frames, rails, etc) is an EGC and not a GEC. It appears to me that an EGC does not necessarily require irreversible splices on it's way back to the main-panel ground bar (might be a good idea, but this is about code requirements). I don't have time to dig up the code sections that brought me to this conclusion. Do others see this differently? If this EGC goes to a grounding electrode, then it is a GEC and does require irreversible splices.
    Thanks for your opinions/info!

  2. #2
    Join Date
    Dec 2012
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    Placerville, CA, USA
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    The PV sections specifically allow a single wire to serve as both EGC and GEC. When this happens, the wire must meet the minimum standards for both uses, including size and continuous or irreversibly spliced.

    You need to look at the whole installation to see whether the wire in question is serving as a GEC. If there is no separate GEC from the array/rooftop, it probably is.
    This comes up most often, IMHO, when microinverters are used.

  3. #3
    Join Date
    May 2011
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    3,810
    Generally I would say that a ground wire from an array is an EGC and doesn't require installations to GEC standards. That's aside from a rare wacko (in my opinion) AHJ I've run into here or there who think that 250.166 requires a GEC from the panels themselves just because they are a power source, or because of some non-scientific idea about lightning.

    The one big bugaboo in this discussion is the awful 690.47(D) in the 2014 (or 2008) code. If your AHJ decides to enforce this against better wisdom then it's hard to argue that the GEC to the array electrode doesn't need irreversible splices, etc.. (Note that GEC rules would not apply to an EGC if it is not the same wire as the GEC to the array electrode.)

    In the 2017 code it is pretty clear that you just need an EGC to a grounding electrode system, which can be the same one that's already serving an existing AC wiring system.

    Per UL if there is a grounded conductor it needs a GEC from the point where it's grounded. This was true of older isolated inverters with a ground-fault fuse, and so the GEC started from the inverter. Most newer inverters don't have a grounded DC conductor and thus UL doesn't call for a GEC and product instructions don't include it.

    Quote Originally Posted by GoldDigger View Post
    This comes up most often, IMHO, when microinverters are used.
    Except that nowadays most micro-inverters are ungrounded on the DC side, so it doesn't anymore. But yes, in the 'old days' this did affect whether the ground wire from the array was considered a GEC.

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