[RE-wrenches] Panelboards in Series - Bus Ratings

[cwarfel]

There may be two tests here.

1)I think you can use 705.12(D)(2)(3)(c)

The sum of the ampere ratings of all overcurrent devices on panelboards, 
both load and supply devices, excluding
the rating of the overcurrent device protecting the busbar, shall not 
exceed the ampacity of the busbar. The rating of the
overcurrent device protecting the busbar shall not exceed the rating of 
the busbar. Permanent warning labels shall be applied
to distribution equipment that displays the following or equivalent wording:
WARNING:
THIS EQUIPMENT FED BY MULTIPLE SOURCES.
TOTAL RATING OF ALL OVERCURRENT DEVICES,
EXCLUDING MAIN SUPPLY OVERCURRENT DEVICE,
SHALL NOT EXCEED AMPACITY OF BUSBAR.

The warning sign(s) or label (s) shall comply with 110.21(B).


2) I think though, that you also need to check the busbar rating of 
panel that is supplying power to this inverter combiner panel so that 
125% of the inverters' output from the combiner panel plus the main 
breaker on the supplying panel  does not exceed the busbar rating of the 
supplying panel.

Chris


On 10/17/2017 5:36 PM, Corey Shalanski wrote:
> *Scenario*
>
>     - 600A *dedicated PV* subpanel w/ (6) 100A circuit breakers, each
>     feeding a 60kW inverter (72.2A rated output)
>     - Subpanel is fused at 600A and connects to a larger main
>     distribution/combiner panel along with other similarly configured subpanels
>
> *Question*
>
>     - Must the main panelboard be sized based on the combined total of OCPDs
>     protecting the subpanels, e.g. 600A + 600A + 600A + 600A = 2400A main panel
>     rating?
>     - Or can the main panelboard be sized based on the combined total of
>     inverter output ratings feeding the panel, e.g. 433.2A + 433.2A + 433.2A +
>     433.2A = 1732.8A main panel rating?
>
> --
> Corey Shalanski
> Joule Energy
> New Orleans, LA
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-- 
Christopher Warfel, PE
Entech Engineering, Inc.
401-466-8978