[RE-wrenches] GridBOSS smart load minimum breaker

[Christopher Warfel]

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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