[RE-wrenches] EG4 GridBOSS AC Coupling

[Jason Szumlanski]

I should also mention that this is an invitation to go down the rabbit hole
of 2020 NEC 225.30 if anyone is so inclined. :)

In my scenario, the power production source for this off-grid home is an
auxiliary building where the inverters and batteries are located. The AC
Coupled solar is on the main house. If I were to run a separate feeder for
the inverter loads and AC Coupled solar, that would be two feeders
"supplying" a separate building. The AHJ argument may become, are any of
the 225.30(A) subsections applicable? They like to think that a condition
of subsection A needs to be met for subsection B to apply, which is not the
case. Two feeders are allowed, as long as they originate from the same load
center (the GridBOSS in this case). As long as the disconnects at the load
end of the feeder are single disconnects per feeder and they are grouped,
225.30(B) is satisfied. You do not need to comply with ALL subsections of
225.30 for an exception to the single feeder rule to apply - only one
subsection.

If anyone thinks I'm misreading this, please let me know. The section has
only existed since the 2020 code, so some of us old-timers still think that
there is a hard rule about a single feeder. I have done a lot of research
on this, and I believe I am interpreting it correctly.


Jason Szumlanski
Florida Solar Design Group



On Fri, Dec 12, 2025 at 5:12 PM Jason Szumlanski <
jason at floridasolardesigngroup.com> wrote:

> For you Wrenches using EG4:
>
> I'm contemplating a system design that would benefit tremendously if I
> could AC Couple PV to the GridBOSS on the backed up load port, but I don't
> see that documented as a method of AC Coupling. I know you can AC Couple up
> to 125A OCPD through a Smart Load port in the GridBOSS, but the AC Coupled
> PV in this scenario would be 400 feet away, and it could be connected to
> the backed up load center at that location (presumably via a feeder tap
> just on the line side of the load center with main breaker installed).
> I'm trying to avoid running a 125A circuit 400 feet back to the GridBOSS,
> and there are some code issues with doing that (multiple feeders
> between buildings being the biggest problem).
>
> I did find a document that allows AC Coupled PV on the load port of the
> FlexBOSS in this scenario, but that does not help me. The FlexBoss connects
> to the GridBOSS through its Grid port, so it's a different scenario.
>
> I reached out to EG4 about this, but I was wondering if anyone here has
> some insight.
>
>
> Jason Szumlanski
> Florida Solar Design Group
>
>
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