Calculating electric service rating, with generation meter

[brycenesbitt]

My local POCO is saying the two situations diagrammed here need different service entrance conductors:

This is PG&E under the Greenbook Section 1.14D:
On the right is a typical residential duplex setup, with solar being back-fed at the bottom of a main panel.On the left is a dedicated back-feed meter.

The left is the setup that exists in my situation.

The POCO says the left requires a 400A service entrance rating, while the right requires just 200A. I can count the numbers in Section 1.14D of the GreenBook and see how they got there. The question is if there is any technical basis for the distinction, or if this is just a lack of consideration of solar in this section?

 

[brycenesbitt]

P&GE's calculation for the left situation
100A because that's the limiting factor of the first panel
+
125A
+
100A
Makes 325A, bump to next size up at 400A.


But the generation meter and the source net to zero, so the actual maximum current, as far as I can tell
is 225A. Or, 80 + 100 if you're talking maximum continuous load rather than rated load.



P&GE's calculation for right figure
100A because that's the limiting factor of the first panel
+
125A
Makes 225A, ok for a 200A drop.

 

[tortuga]

Yeah its bizarre, I run into this kinda thing often.

 

[electrofelon]

Even without the discrepancy of the location of the solar interconnection, it's kind of weird to me what business it is of theirs to talk about NEC service rating. Any equipment they are sizing I would think they would size a lot less than the sum of those breakers

 

[brycenesbitt]

Even without the discrepancy of the location of the solar interconnection, it's kind of weird to me what business it is of theirs to talk about NEC service rating. Any equipment they are sizing I would think they would size a lot less than the sum of those breakers

They DO impose requirements on the NEC side, indeed.

But here they're talking about the service mast, from the gutter to the drip leg. That is in their purview, they're just (as far as I can tell) calculating it wrong because their holy book said something that did not apply in this case. So they want a 400A gutter and 400A mast for what seems to be 200A service.