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Bonding for Roof Top Solar Array

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    Bonding for Roof Top Solar Array

    Roof top solar array: Enphase microinverters kicking out AC (two conductor). Solid copper EGC bonded to racks. EMT sleeve runs from East to West side of roof and between strings on west side. EMT does not terminate in a box (i.e., open ends). Obviously the EMT runs must be bonded to the EGC. Solar PV wires also require splicing in JBoxes so that sections of large strings are run in parallel. The plan is to run all EGC solid copper to one jbox with a pass-through into attic. To avoid additional holes in roof, I am using EMT clamps attached to the solar racking. The JBOXs for splicing solar wire are polystyrene. I plan on attaching them with either plastic or metal screws to aluminum brackets, with brackets bonded to the solar racks with the approved mounting screws for the microinverters. Here are my questions:

    EGC Questions:
    1. Can multiple EGCs solid copper wires terminate in jbox/pass-through to a lug with one solid copper wire from that lug running passed through to combiner box in attic? (I guess this would be referred to as a reversible spice in a jbox)
    2. Do I need to bond the EGC to an EMT sleeve on both ends, or can I just bond it to one end?
    3. Can I use an insulated green EGC and just strip the insulation where bonding?
    4. Do I have to, and can I, run the EGC (bare or insulated) inside the EMT with the PV AC wire?
    5. The bonding bushing for the EMT has a lug on the outside of the bushing. If I run the EGC inside the EMT, after it goes through the ground lug of the bushing, then I will have to loop it backwards to get into the EMT tubing. Is there a better/standard way to address this (e.g., it would be nice if the lug were in line with the tube opening)? Or does one simply loop it back through?
    6. Does a hand made aluminum bracket attached with approved mounting screws satisfy bonding requirements.

    PV splicing JBOX Questions:
    1. No EGC needed? (its plastic)
    2. If I attach the polystyrene jbox to the aluminum bracket metal screws, then those screws would be bonded to the aluminum bracket (in theory), and the bracket is bonded to the rack. In addition, the boxes have a plastic plug to seal the mounting holes such that there is no exposed metal inside the box, even when using metal screws. Are there any additional bonding requirements other than the bracket/EGC bonding if I use metal screws to attached a plastic JBox?

    Also - these are NEMA4 JBOXs. It seems reasonable that I should create weep holes in case they leak. Otherwise, in the very unlikely event that they take on water, it has nowhere to go. Thoughts on this?

    #2
    Sounds like you could use help from someone with more electrical experience.

    Bond the copper EGC to the racking as directed by the racking manufacturer.

    Pull your wire through any open ended chases, leaving enough slack to land it in the grounding bushing lay-in lugs as you go around dressing up your wiring. You could bonding only one end if you wish, unless you run into that weirdo inspector who still thinks they are actually GECs. (They are not.)

    Wherever you bring multiple EGCs to a box, you are required to splice them all together. There should be no need to run more than one EGC in one conduit from a box to another box, including the combiner. Your splices do not need to be irreversible unless you run into that same weirdo inspector.

    You may run bare ground wire in EMT. I think the size allowed for solar arrays was increased to 6awg in the 2017 NEC. Some inspectors may require 6awg EGC for all exposed EGCs on the racking.. You can probably run insulated wire, but why would you?

    Wherever you use plastic boxes you need grounding bushings on the conduit to provide continuous bonding. Any EGC in the box can be landed on any of those lugs.

    Plastic screws? What?

    Probably a good idea to put weep holes in boxes on the roof. It voids the NEMA4 rating but that rating is not required. Also a good idea -code requirement actually - to install duct seal in the conduit that goes through the roof.

    Did I miss anything important?

    Comment


      #3
      Reply

      Thank you for responding. I really appreciate it. It's difficult to find answers to some of this.

      Originally posted by jaggedben View Post
      Sounds like you could use help from someone with more electrical experience.
      Yes. I will have a licensed electrician review the final product and de-rate my main breaker accordingly. However, I am the same guy that had my subpanel wired by a lic. electrician with ground and neutral reversed (the electrician and the panel :-) - so trust but verify.

      Originally posted by jaggedben View Post
      Bond the copper EGC to the racking as directed by the racking manufacturer.
      Check - that's the plan.

      Originally posted by jaggedben View Post
      Pull your wire through any open ended chases, leaving enough slack to land it in the grounding bushing lay-in lugs as you go around dressing up your wiring. You could bond only one end if you wish, unless you run into that weirdo inspector who still thinks they are actually GECs. (They are not.)
      As a result there will be a small loop back to get to ground lug. There are three sets of racks. Each will have a solid copper EGC and they will all eventually land in the solar pass-through box. EMT is only used to get from the two outer arrarys to under the one central array under which the pass-through box is located. Wiring under the arrays is not in EMT. Therefore the wires (including the EGCs) run through cable glands into the solar pass-through box.

      Originally posted by jaggedben View Post
      Wherever you bring multiple EGCs to a box, you are required to splice them all together. There should be no need to run more than one EGC in one conduit from a box to another box, including the combiner. Your splices do not need to be irreversible unless you run into that same weirdo inspector.
      For the splice I assume that landing the EGC in the lugs in the solar pass-through box will suffice.

      Originally posted by jaggedben View Post
      You may run bare ground wire in EMT. I think the size allowed for solar arrays was increased to 6awg in the 2017 NEC. Some inspectors may require 6awg EGC for all exposed EGCs on the racking. You can probably run insulated wire, but why would you?

      Wherever you use plastic boxes you need grounding bushings on the conduit to provide continuous bonding. Any EGC in the box can be landed on any of those lugs.

      Plastic screws? What?
      The EMT does not terminate in the JBOXs. JBOXs are separate with cable glands. This was intentional because when running EMT into a JBOX you increase the potential of leaks (at least I assume that you do because the EMT is running over a roof ridge and will have rain hitting it that will then flow downgradient to a termination point. With open ends no water will enter the EMT. With a connected JBOX it could).

      Originally posted by jaggedben View Post
      Probably a good idea to put weep holes in boxes on the roof. It voids the NEMA4 rating but that rating is not required. Also a good idea -code requirement actually - to install duct seal in the conduit that goes through the roof.
      Check on weeps. The expensive pass-through box was designed for solar and is flashed. Pass-through conduit sits under a cover and has a seal of some sort.

      Originally posted by jaggedben View Post
      Did I miss anything important?
      I think that you got it all - fantastic.

      Comment


        #4
        Last time I babysat an inspection for one of my installs in Davis the inspector was clearly more interested in Smokies&CO and low flow toilets than the array. That's not a joke, make sure your toilets are labeled low flow or you'll likely fail.

        1. Follow JaggedBen's advice.

        2. Typically when I run conduit between arrays as a chase for PV Wire/Raw Q cable I will bond both ends with bare copper to the racking and use the EMT as the EGC and not run a dedicated wire EGC through the conduit. For lots of reasons our systems are typically small (1 or 2 Enphase branches/1 or 2 strings of SolarEdge), so we are bending mostly 1/2" EMT. Pulling raw Q through 1/2 isn't so bad, but still will likely still require a fish tape for a complicated series of bends. Pulling Raw Q and an insulated stranded #8 EGC isn't much fun at all through 1/2" EMT, and it's just miserable pulling bare #8 if you have anything more than a completely straight run. Bond both ends and use a high quality Coupling/Ground Lug and I feel really good about that solution.

        Sac City is really the AHJ that's the most difficult within a 50 mile radius.

        Comment

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