[RE-wrenches] GridBOSS smart load minimum breaker

Fri Jul 24 16:47:57 EDT 2026

It just hit me - this must be a carryover from their older version of the
GridBOSS that did not accept standard Eaton BR circuit breakers. They sold
the original GridBOSS v1 with a breaker kit with B3S1 breakers manufactured
by BSB Electric. You had to buy the breakers from EG4, and they did not
offer 15A or 20A breakers for these circuits. Intiially they shipped the
breakers with the GridBOSS. I remember thinking how wasteful it was for
them to send each unit with a bunch of breakers that we didn't use. And
then they suddenly started selling the GridBOSS without the breaker kits,
and I was derailed on a job, not realizing they had made that change.

Here is the excerpt from that manual:

[image: Image 2427.jpg]

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 4:33 PM Jay <jay.peltz at gmail.com> wrote:

> Is it possible they have the UL listing with those specific breakers?
>
> It’s just a breaker. As long as it’s physically compatible in mounting
> electrically it’s fine.
>
> Jay
>
> On Jul 24, 2026, at 2:25 PM, Jason Szumlanski via RE-wrenches <
> re-wrenches at lists.re-wrenches.org> wrote:
>
> 
> 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 (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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