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  • Breaker for PV string

    I've purchased some solar equipment from Wholesale Solar in CA. They made recommendations for accessories I would need, and I've accepted their recommendations, purchased the entire package, and am installing it. However, one thing struck me as odd, and I've actually heard other (reputable) sources say the same thing.

    My PV modules are tied in strings which have Voc of 90V and Isc of 8A. Each string is tied to a 15A breaker in the combiner box. So under short circuit conditions, the strings are limited to 8 amps. Under what conditions could the breaker ever trip?

  • #2
    Back feed faults from the utility, and accidental contact with other circuits. All source circuits have to have over current protection device installed to protect the wiring.
    MSEE, PE


    • #3
      You could have gone with a 10 or 12 amp, but as Dereck said, what you're really protecting against isn't the max current from the panel string, but something outside that arena. You could have used a 20 also. The wire from the panels is normally #10, and rated for about 30amp, so you just really want to be under that, and 15 is fine.