[RE-wrenches] GridBOSS smart load minimum breaker

Fri Jul 24 16:22:15 EDT 2026

We don't have #10/2 Romex on the trucks usually. It's most convenient to
run #14 or #12 to a light fixture usually (if not running it in conduit).
And some fixtures are not very friendly with a larger wire or cables.

I can't think of any logical reason that a lower rated breaker would be a
problem. I truly think they just didn't think it through very well when
writing the documentation. The lack of 25, 35, and 45A breakers is a prime
example. Surely these are okay, right?

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 Fri, Jul 24, 2026 at 1:00 PM Christopher Warfel via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> Would it make sense just to upsize the conductor for this short run?
> On 7/24/2026 5:47 AM, Jason Szumlanski via RE-wrenches wrote:
>
> 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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> --
> Christopher Warfel, PE
> ENTECH Engineering, Inc.
> PO Box 871, Block Island, RI 02807
> (401) 447-5773
>
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