[RE-wrenches] 705.12.B.(3) (b) the over-current device protecting the bus-bar

[Christopher Warfel]

I think it is *705.12.B.(2)(3) (b) in 2017. *The inverter's OCPD must be 
at least 125% of the maximum continuous current output of the inverter. 
That is 40A x 1.25 = 50A.

Then, the sum of the supply side sources, which is the Main Breaker 
_rating _PLUS 125% of the sum of the inverter(s)' _maximum continuous 
current output _must not exceed 120% of the busbar rating.

With 200A busbar rating, you have room for 200 x 1.2 = 240A of supply 
side amperage as defined above.  240 - 200 (assumed main breaker rating) 
- 40 x 1.25 = -10A.  This means you have exceeded the allowance under 
this section.  Options are to decrease the Main Service breaker if a 
load calculation allows it, or the supply side option. I would take 
apart the Main Service Panel and get its rating. I often find a 200A 
panel has a 225A busbar. Then you would be ok interconnecting as you 
have thought.   Chris

On 6/5/2019 10:33 PM, Darryl Thayer wrote:
> Can this overcurrent protection be the current limit of the inverter? 
> I was challenged by a licensed professional engineer he said it is the 
> circuit breaker, I said it is the inverter.  I said I can put a 50 amp 
> breaker into the circuit panel with a 200 Amp bus, (125% for 
> continuous)  on a 40 amp max output inverter.  I.e  a 9.6 kW inverter 
> on 50 Amp breaker bus bar protected by inverter output.
>
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