Friends:
I have heard, but I have not researched myself, a provision in the code
where one could dedicate a panel to be an "AC combiner" to collect the
outputs of multiple inverters. You would not install any branch circuit
breakers and thereby eliminate the need to comply with the 120% rule. This
scenario has never occurred in any projects we have designed, which is why
I have not researched the code in this regard.
For a theoretic discussion, however, I wonder this: Even though you have
eliminated branch circuits from the equation, you still have the potential
to overload the buss bars in or the feeder to the breaker panel in
question. If a fault occurs in the panel or feeder, you still have sum of
the feeder breaker and the inverter breakers feeding the panel and the
feeder in excess of what either is rated for. Is this not a
concern? Faults can occur other than in branch circuits, faults such as a
wrench dropped across the buss, backhoe fade, defective inverter breaker or
compromised insulation. Such a fault could cause catastrophic failure of
the panel and/or feeder. Has anyone else pondered this question?
William Miller
PS: I realize a fault in the feeder means that you have fault current
below the feeder rating from either direction, but what about at the point
of the failure?
Wm
At 09:38 AM 1/22/2012, you wrote:
Hi Nick,
I see (2011) 705.12 (d) where it talks about " supplying branch circuits
as the area where it changes.
ie w/o branch circuits then all circuits are protected by the breakers as
long as the main buss isn't exceeded by the solar input of course.
But in putting in that metering device plugged into a outlet, now you have
a branch circuit and hence the need to comply with 705.12 (D) 2.
But I could be wrong.
jay
peltz power
On Jan 22, 2012, at 8:36 AM, Nick Vida wrote:
That is very interesting Jay, do you have a code reference for no derate
needed for your solar accumulation panel?
Thanks,
Nick Vida
btw- Rich, thanks for Bernie Sanders.
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