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A happy exception to "the AHJ is always right."

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  • A happy exception to "the AHJ is always right."

    Among the collected wisdom that I've appreciated here is the statement, "The AHJ [authority having jurisdiction, i.e., electrical inspector] is always right." But I got dinged on something so weird during a recent inspection that I figured it would be worth a follow-up call to the inspector to talk about it.

    He'd written, "All DC circuits installed inside of structure shall be installed in metallic conduit." The 8 AWG wires going from my newest charge controller to the Outback 8048 GSLC are just nailed (with proper non-conductive electrical staples, of course) to the oak plywood mounting wall inside my solar equipment shed, with no conduit. It's a locked metal shed whose only purpose is to house my solar equipment, and having to run those wires inside conduit there seemed just crazy to me. If the output of a charge controller constitutes a "DC circuit" that has to be enclosed in conduit, where does it stop? How about the 4/0 battery cables?

    As I grumbled to myself about this while reading the inspection report and looked at the cited regulation 690.31(G) of NEC 2017, I realized there was some language in the code that neither the inspector nor I had noticed:

    Where PV system DC circuits run inside a building, they shall be contained in metal raceways, Type MC metal clad cable that complies with 250.118 (10), or metal enclosures from the point of penetration of the surface of the building to the first readily accessible disconnecting means.
    Do you see it? It's that last phrase, "from the point of penetration of the surface of the building to the first readily accessible disconnecting means." Well, I do have the PV wires running inside 1/2" EMT from the array to the PV disconnect. It's only after the PV disconnect that I have exposed (insulated, of course) wires.

    I called the inspector at the number listed on the report, spoke politely and calmly, and said the code was understandably confusing on this point but that wanted to point out some language that clears things up. I then read him the phrase about the requirement applying for circuits from the point of penetration to the first readily accessible disconnecting means. "Remember the PV disconnect I have down in the lower left for that array? There is EMT leading from the array right to the input of that disconnect."

    He was very reasonable and said, essentially, yes, this looks like a case where it really is legit the way it is. He added something about there being a lot of different pieces in a PV system and it's easy to miss something, and I replied (sincerely) that the code language was pretty confusing and thanked him for making the change to the report.

    One phone call saved me an afternoon of powering down the system, pulling out some fat wires, knocking out some more holes in the charge controller and GSLC, and installing a length of flex conduit! My THHN insulation will continue to work just fine for this new CC inside what amounts to a really big metal enclosure, as it has for my other two inspected charge controllers for nearly a year now. That would have been a really frustrating bit of work to do.
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