705.12(B)(2)(1) Back fed breaker

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Twisremo

Member
Location
florida
Occupation
electrician
A meter/main with a 200 amp main breaker with a backfed 40 amp breaker for solar, the feed thru lugs go to a 200 amp rated MLO sub panel with 4/0 SER.

I've been seeing several municipalities requiring the feeder size or overcurrent protection device being shown in the plans in compliance with the title mentioned code, just wanted to get some thoughts on this. I ask because the referenced code is for feeder connections and the solar is connecting to the busbar(via breaker).

Thanks
 
J

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
How is the 4/0 feeder and 200A subpanel protected from drawing 232 amps? (Is that 4/0 aluminum or copper?)

Is the solar breaker at the opposite end of the busbar, or are the feed-through lugs taking up that spot?

A busbar can be a feeder.
 
W

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
This is subject to the 2017 NEC, which it appears is current in Florida?

Under the 2017 NEC, feed thru conductors are not explicitly addressed in 705.12(B)(2)(3). So it is arguable that you can't use the 120% rule in the main panel. You could move the 40A solar breaker to the subpanel, in the position opposite the main lugs, and then use the 120% rule for both panels.


Under the 2020 NEC, there is a not super clear new section on feed thru conductors, 705.12(B)(3)(6). I think it would allow the configuration you describe if you add a 200A OCPD just downstream (away from the grid) of the feed-thru lugs. So you could perhaps appeal for that allowance.


Cheers, Wayne
 
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