supply side combiner connection

I have a project that will have 8 inverters 240V. There will be 90kW of modules installed. The site has a large generator and we need to interconnect between the meter and the transfer switch. I can get two cables from each line to the transfer switch. So I need to either combine all 8 inverters or make two groups. The total of the 8 is a max 375A. Does anyone know of a source for a combiner with disconnect and OCPD? Could I just backfeed a breaker panel?
 

McMac

Member
That is exactly right. MB load center properly identified as an AC Combiner and warning labels not to add loads.

Check with utility and ahj to make sure it doesn't have to first be routed through a knife blade style "safety switch" first, as most of our utilities around here require for disconnecting means.

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ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
That is exactly right. MB load center properly identified as an AC Combiner and warning labels not to add loads.

Check with utility and ahj to make sure it doesn't have to first be routed through a knife blade style "safety switch" first, as most of our utilities around here require for disconnecting means.

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An AC combiner can compliantly contain loads as long as the bus is qualified under one of the pertinent subsections of 705.12. Your AHJ may not like it, though.
 

McMac

Member
An AC combiner can compliantly contain loads as long as the bus is qualified under one of the pertinent subsections of 705.12. Your AHJ may not like it, though.
Yes, subsection 'c' of 705.12(B)(3) allows loads such that the sum of all load and supply breakers except the main breaker do not total more than the bus rating. Premade labels exist with the appropriate warning verbage which is close to what I just said.

Subsection 'b' ("120 Rule") and 'a' of are very unlikely to happen in a Combiner Panel.

Typically I will use 705.12(B)3(c) to allow for powering monitoring equipment from the AC Combiner. And while the NEC says to label as stated above, depending on the facility I will still add in the "DO NOT ADD LOADS" label to try and prevent unqualified persons from adding too much down the road.

See attached


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