Mayfield Renewables Code Corner: 2020 NEC 705.12(B)(3)(6) Load-Side Source Connections

In this edition of our Code Corner video series, our Founder and CEO Ryan Mayfield is joined by Senior PV Designer Ry Heller to look at NEC 702.12 applications for load-side source connections.
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[@user-xv5mc6tu8d]

If the subpanel is

[@MayfieldRenewables]

Yes, that is a very common interpretation.

[@safetythirdified]

What am I missing here with the language of 705.12(B)(3)(1)? The SUM (additive, correct?) of 125% of power source (solar circuit), ok. 32Ax1.25=40A "and" ( sumed with) the rating of the overcurrent device protecting the busbar (200A), if my math is mathing is a total of 240A. By their text, this is exceeding the ampacity of the busbar no matter what the scenario is.
Edit: Still not sure why that section is even relevant, or when it could ever apply, but then I read down to 705.12(B)(3)(2), and that section fits this example that makes sense to me.

[@MayfieldRenewables]

For the example you provided, 705.12(B)(3)(2) would apply. 705.12(B)(3)(1) would come into play if, for example, you were interconnecting 20A of PV to a 225A busbar with a 200A main breaker. In that scenario, 225A < 200A + 20A and the PV breaker could be placed anywhere along the busbar. This is a very rare scenario.

[@davem5392]

Would putting a breaker in the main panel to feed the sub panel be the easiest solution or am I missing something. If they have a 200 amp service I can’t imagine a sub panel needing more than 100 amps. So feed dub with 100amp double pull from main panel

[@ryanmayfield2728]

If the PV conenction were made as a load side connection in the main and the sub was protected with a breaker, I would say yes, that works well. As long as that feeder is properly protected from overload, that would accomplish the same thing as providing an external OCPD. In the case of needing more than 100A this may be difficult due to breaker sizing in the panel though.

[@kimandylawrence4199]

Very good video. I see that you didn't address the possibility of using 705.12(B)(3)(3) for protecting the busbar in the supplying panelboard even though the code allows it.

[@MayfieldRenewables]

Yes, you are correct. When installed according to (B)(3)(6), the rules of (B)(3)(1) through (B)(3)(3) would apply to the downstream subpanel.

[@danlezama30]

Putting the breaker by the supply side (main service panel) is overkill. These regulations are getting insane.

[@ryanmayfield2728]

I'd say it's all about protecting thos conductors so there are certainly multiple ways to accomplish it.