Parallel String Brain Teaser [RE-wrenches]

[Bob-O Schultze, Electron Connection]

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Bill and All,
In my experience, sizing an overcurrent device at Isc X 1.56 per NEC 
on the PV side of the CC pretty much turns whatever you are using 
into a disconnect and nothing more.
Bob-O


>Got me thinking for a few seconds, but after reading it again, I don't think
>it means what you want it to mean. I'm not sure how being supplementary is
>relevant to the fact that standard fuses cannot be run at more than 80% of
>their rating continuously. We could get into a long discussion about the
>rightness and wrongness of this, but field experience says that if you try
>to use a fuse rated at 1.25 x Isc it will blow occasionally, if you use 1.56
>you almost never have a problem. Might be dumb luck, or it might be design.
>Many folks historically just put the 60-amp breaker on the whole array and
>called it good--does that make it right?
>
>Calling something one source circuit under 50 volts is nomenclature and by
>no means absolves us of the requirement to fuse modules.
>
>Bill.

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