Ground faults / NEC changes for 2005 [RE-wrenches]

[William Miller]

Steve:

It is a fallacy to believe that positive voltages are the only source for
current, fault or otherwise.  In this case, when the positive at the PV
array was grounded, the negative PV lead was forced to become 48 volts
lower than the battery negative.  (When the PV negative was connected, to
the negative buss, it was at 0 volts, but it was pumping the entire SC
current through it.  When it was disconnected, it went to - 48).

The negative can not be disconnected by a breaker as there is no breaker
installed in that lead, so we have current in a device that was "shut off."
 This was the negative voltage trying to get to the ground rod, back into
the building and back to the shorted positive PV lead.  The negative was
one leg of the circuit, the ground and structure the other.  Get it?

William



At 10:40 AM 11/15/02 -0800, you wrote:
>
>You stated that all those breakers were manually off and still arcing was
>possible on the board when a screwdriver was applied to it.  this suggests
>an additional source of + battery or +PV was available to the board.  Were
>there a temp sensor or the external battery current shunt connected to the
>board that could have come in contact with + battery voltage?  Any other
>wires?  (I would expect a larger wire, and not the temp sensor, would be
>required to bringing that much current)
>Steve Willey       steve at backwoodssolar.com


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