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Thread: solar passthrough compliant?

  1. #1
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    solar passthrough compliant?

    hello all-

    been a long time...

    im in California under the 2016 CA code

    please see the attached document- has anyone seen this type of solar install before? beside the obvious potential of "panel listing violation" do you believe this is NEC complaint, or no?

    thanks in advance for you expert opinions!
    Attached Images Attached Images

  2. #2
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    It is compliant. Their letter is incomplete though. They really should be referencing 705.12(D)(2)(3)(c) and promising to put a label with exactly the wording required in that section. There is no code reason to bolt anything to the deadfront, although it doesn't strike me as a listing violation worth bothering over if done professionally.

    We have only done 'Hawaiian Tie-ins' when the main panel is just one or more main breakers, but what they propose is compliant as well.

  3. #3
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    any other thoughts?
    it is a strange one... I have always pictured that rule as adding a 20A solar circuit to a 100A panel with 80A of existing loads. not a 200A sub with a 40A solar circuit feeding a 100A panel with a 100A main...

    that would mean for instance-

    with a 200A service, I could relocate all my circuits to a 400A subpanel and backfeed a 200A breaker (with 80A solar load) on the main... not what I ever pictured, just doesn't seem correct. I cant seem to wrap my head around it
    Last edited by mayjong; 05-21-19 at 06:04 PM.

  4. #4
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    What seems not correct about it?

    My understanding is that the concerns are busbar heating in fully loaded panelboards. The CMP came up with three rules to avoid that, each of which have a certain logic based in electrical theory. By relocating load breakers that probably add up to way more than 200A out of the main panel, the installer is protecting that panel in one of those ways.

    Another way to look at it: if you had a 200A fused disconnect feeding a 400A panelboard, you wouldn't find that wrong. (Or would you?) The installer is proposing to essentially turn the existing panelboard into a disconnect and no longer really utilize its function as a panelboard.

    It's also my understanding that 705.12(D)(2)(3)(c) was put in largely to legitimize 'AC combiner' panels for multiple inverters without having to make them rated almost twice as much as the output. But that's kind of neither here nor there.

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