Yet another grounding question

This deals with multiple bonded 8 foot deep ground rods, 16 feet apart, and in an East-West line 8-12 feet south of the house. On the east-most rod will be the ground coming down from the roof-mounted array. Sixteen feet to the west of that will be the ground from the PV combiner, containing a lightning arrestor, to the second rod. West of that will be the ground for the FLEXpower One to a rod shared with the AC grounds. Alternatively, the AC grounds could go to yet a fourth rod another 16 feet west of the FP1 ground rod, depending on where I put the AC main panel, also bonded to the other ground rods. For what it's worth, the single DC negative to ground bond is in the FP1 through an 80A GFDI.

Will this likely pass inspection without a lightning-carrying ground conductor in the PVC conduit between the PV combiner and FLEXpower One entrance?

Thanks!

Comments

  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Yet another grounding question

    it probably would pass if i read what you are saying correctly as the nec insists the ground lead go back into your dwelling where it is then allowed to eventually go to ground via the main service entrance box. the nec does allow for a separate ground rod for the pv grounds, but does not insist on it being grounded to a ground rod externally. i disagree with running the ground wire into the dwelling and i am a firm believer in a direct lightning ground path to a ground rod, but as it is due to the nec's insistence on running the ground wire into the home a proper external electrical ground path can cause ground loops by allowing 2 paths to ground. i differ with the nec's insistence on bringing a ground lead into the dwelling from outside as i believe it should only go straight to the main utility ground rod outside. to me it doesn't make sense to allow lightning a path into a dwelling, but that is the nec's ruling which in turn often becomes local law.

    if it were me i'd put the external pv ground rod in and bond it underground with the utility ground rod as well as the required ground lead going into the house too to meet nec regs. after inspection i would disconnect the ground lead going into the house from the outside.

    of note: you should know all ground rods should be bonded together underground with #6 or better bare copper wire. i recommend burying it at least 1ft down so as to avoid accidental cuttings of the wire.
  • Moe
    Moe Solar Expert Posts: 60 ✭✭
    Re: Yet another grounding question

    Thanks, Niel. Your past posts on the subject made me consider this. I've considered bonding the ground rods with 2" x 0.032" copper strap for lower impedance between them. Hopefully, that's acceptable by code.

    I'll know more when I get the code book, but I have another question. The battery connections will be 2/0, which would imply 2/0 required for the FP1 ground. Somewhere I read #6 would do if it's the only thing connected to a ground rod. Does that "only thing" exclude bonding wire to other ground rods?

    Thanks!
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Yet another grounding question

    i would not use strap underground. it is more apt to corrode and break than a single solid wire. impedance does not need to be considered as the bare copper wire is also acting as an extension of the ground rod with its contact area to the soil.

    as to the nec, i don't believe they actually address or care about bonding ground rods underground. there is certainly nothing wrong with going to bigger wires for bonding the rods and i originally only went with #6 as a minimum due to the corrosiveness of soils as otherwise i would've said #8 as a minimum. going larger is good if you can afford it and it must be bare copper wire, for insulated wire would defeat the wire's contact with the soil and lessen the effective grounding potential to only the rods themselves. it can be done with the insulated wire, but moisture would still wick into the wire itself and depending on the insulation the soil may break down the insulation too.