Inspector will not accept multi back-feed breakers

JoeNorm

Senior Member
Location
WA
So we just installed a 400 amp panel with a 200 amp main breaker and landed multiple "source" breakers from solar inverters.

Inspector will not pass this project until we combine all the source breakers in a combiner panel and land one dedicated breaker in the main panel.

He is referencing 705.12(B)(1) Dedicated Overcurrent and Disconnect. I interpret this as meaning that every inverter should have a dedicated breaker, but not necessarily that they cannot all be landed in one panel.

What do you think about that code interpretation?

thanks
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
So we just installed a 400 amp panel with a 200 amp main breaker and landed multiple "source" breakers from solar inverters.

Inspector will not pass this project until we combine all the source breakers in a combiner panel and land one dedicated breaker in the main panel.

He is referencing 705.12(B)(1) Dedicated Overcurrent and Disconnect. I interpret this as meaning that every inverter should have a dedicated breaker, but not necessarily that they cannot all be landed in one panel.

What do you think about that code interpretation?

thanks
I don't know that there is an explicit proscription in the NEC for having multiple points of interconnection for PV systems, but most (all?) of the AHJs we deal with don't allow it for residential systems. The 120% rule in 705.12 says that the interconnection must be at the other end of the busbar from the utility feed, but it is debatable whether two breakers can be equally at the other end if they are across from each other in the last slots. Rationally and again IMO, what the language really means is that there should not be any loads on the other side of the PV interconnection point on the busbars from the utility feed, but that's not what it says.

The bad news is that you are probably at the mercy of the AHJ, and if they want you to combine inverter outputs onto one breaker in the MDP, that's what you will have to do. FWIW, we always do it.
 
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JoeNorm

Senior Member
Location
WA
I am pretty convinced the wording allows for it but of course you're right about having to listen to the AHJ.

I believe it to be worth the time to convince him otherwise because I think it is very handy to be able to eliminate the combiner panel when there is an opportunity to do so.

Like you say, if every source breaker is opposite the utility feed as much as it can be, how is that any different from it being in the one most opposite position? If were worried about busbar "hotspots" wouldn't spreading the feed from the solar out along the busbar be better?

I just have a hard time with things that are not rational.
 

pv_n00b

Senior Member
Location
CA, USA
The intention was always to allow multiple OPCD in a panel for interconnections, as long as the inverters were not sharing the OPCD with a load. You will note that in 2017 in 705.12(B)(1) the word "each" was added because too many AHJs were misinterpreting this. So each interconnection of one or more PV inverters can use a dedicated OCPD. The number of interconnections is unlimited.
 
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