[RE-wrenches] GridBOSS smart load minimum breaker

[Jason Szumlanski]

My read: EG4 likely omitted 15A and 20A because these are contemplated as
high-current smart load or AC-coupled inverter ports, not branch circuit
protection for small loads. The GridBOSS is sized for things like EV
chargers, HVAC, water heaters – not standard household receptables and
lighting. They expect those to be regular backup loads. The biggest example
I have to support the need to shed a 20A load is a pool pump.

Anyway, when I use a GridBOSS for an off-grid installation, I almost always
use Port 4 for a 15A multiwire branch circuit to support a convenience
outlet and lighting for the area on one leg and a generator battery
charging circuit on the other leg. I see no issue with it.

One thing that supports my theory that the breaker ratings are the maximum
supported per port is that the ratings in the table overlap. Looking at the
table, on line 1, port 1 supports 90-125A breakers, then the table goes on
to support 30-80A breakers for port 1. The whole tables is a confusing
mess. And what about 35A breakers? 45A? These are common for some
mini-split units. They are not in the table, but surely would not be a
problem.

EG4 needs to revamp this table for clarity.

P.S. I have started using Port 1 as the main load port for smaller off-grid
jobs without even using the 200A backup load port. I just set port 1 to
operate 24 hours a day. This way, you don't need additional overcurrent
protection from an external main breaker. The downside is that the manual
bypass becomes non-functional, but otherwise it has worked out well for me.


Jason Szumlanski
Principal Solar Designer | Florida Solar Design Group
NABCEP Certified Solar Professional (PVIP)
Florida State Certified Solar Contractor CVC56956
Florida Certified Electrical Contractor EC13013208




On Thu, Jul 23, 2026 at 9:24 PM Dave Tedeyan via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> Hi All,
>
> I will soon be installing one of these in a detached shed, where it would
> be useful to have a light installed. There will be no panel in there other
> than the GridBOSS, inverters and batteries. The manual says that the
> smallest breaker size that is supported is a 30a breaker. See table below.
>
> I emailed their tech support to ask if there would be a problem with a 20a
> breaker. They gave a very basic answer pointing me back to this same table,
> and then recommended to add a subpanel, and then run a 20A circuit from
> there. That seems a bit overkill for a light. I cannot see why if a 30A
> breaker is allowed, a 20A breaker would not be allowed. It is just a simple
> Eaton breaker. Am I missing something here?
>
> Cheers,
> Dave
>
> [image: image (4).png]
>
> --
>
>
> Dave Tedeyan, P.E.
> Owner | Sungineer Solar
> p: he | him | his
> a: 1653 Slaterville Rd. | Ithaca, NY 14850
> w: www.sungineersolar.com <http://www.sungineersolar.com/>
> c: (607) 270-0370
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