[RE-wrenches] AC combiner panels [was Gray code area]

[bbassett at hei.net]

Bill,

How does this effect using an AC panel to combine inverter outputs? It
sounds like so long as there are no load breakers it can be used up to
it's bus rating with inverter breakers. Or is what you are talking about
only applicable to the tie in point or service entrances? I don't find the
code quite clear on this point.

I've been assuming that the AC combining panel bus has to be rated for the
sum of the circuits from both directions. ie: 3 inverters feeding 30A
breakers = 90A, and a 90A breaker in the next up tie in panel = 180A so a
200A (actually only 150A calculated with 120% over) bus rated panel must
be used. I would be happy to be wrong and it would only need a 100A panel
now (actually only 75A calculated with 120% over).

Also would 690.64(B)(7) preclude the use of the 120% factor if the
panelboard is like the Square D 6 space unit with AC hot feeds from
opposite ends of the panel making a 2 pole inverter breaker never feeding
the opposite end on both bus bars?

Brad Bassett
AEE Solar


Bill says:

I may have misunderstood something here, but 690.64(B) is a load side
connection section and must have loads in order to be considered load
side. With no loads on the line side of the service disconnect, we are
simply creating another service disconnect (see previous discussions on
numbers of disconnects and service definitions).