Chris:
The issue is not so much the voltage as the amperage. Utility power has
amperage capabilities that far exceed the rating of the usual over current
protection devices. In a fault, the current is temporarily very high,
opens the OCPD and the problem is resolved.
With PV, the power is current limited and we want to draw 100% of the
amperage available, so OCPD must be sized smaller than the available
ampacity of the string, otherwise the OCPD would trip every sunny day.
This is the crux of this very serious problem, and the reason PV wiring
should aspire to the highest standards. There is no breaker that will
protect your wiring.
(OCPD is required and is useful in preventing parallel strings from
back-feeding each other in a fault condition.)
William Miller
At 11:08 AM 10/22/2012, you wrote:
Maybe we should reduce our household voltage to 70V also, it would be save
and you could fuse it...
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