705.12(A)

[wwhitney]

Use the term however you want but please stop telling me that the way I use it is wrong.

I don't mean to suggest that you are using the terms "wrong." I'm just suggesting that when you post about requirements, it would be helpful if you differentiate between NEC requirements, which will apply to basically all US readers of this forum (although interpretations of some aspects of the NEC may differ across jurisdictions) and POCO requirements, which can vary widely across locations. In this thread, the OP is asking about the NEC requirements, so additional requirements the POCO makes are not particularly relevant to the OP's question.

What you have described is a 705.11 interconnection, not a 705.12 connection as we were discussing;

Oops, I was wrong, thank you for the correction. I was thinking of the 2017 NEC, where 705.12(A) is supply-side interconnections, but the OP clearly says 2020 NEC.

Now I mostly agree with you. You could do still do the following if you wanted, although I imagine it wouldn't be so common, but it would result in a multiple 705.12(A) disconnects and a single PV meter. Namely in order moving away from the utility: breaker supplying a feeder - feeder is tapped (or just spliced, depending on the ampacity) to a load panel - feeder continues to a PV meter - multiple taps (or splices) on the load side of the meter to multiple 705.12(A) disconnects. [Edit: the breaker on the utility side of the PV meter is not a 705.12(A) disconnect as it also kills power to the load panel, so it is not "dedicated" to the interconnected sources.]

Cheers, Wayne

 

[ggunn]

I don't mean to suggest that you are using the terms "wrong." I'm just suggesting that when you post about requirements, it would be helpful if you differentiate between NEC requirements, which will apply to basically all US readers of this forum (although interpretations of some aspects of the NEC may differ across jurisdictions) and POCO requirements, which can vary widely across locations. In this thread, the OP is asking about the NEC requirements, so additional requirements the POCO makes are not particularly relevant to the OP's question.

Thank you for your suggestion; I will keep it under advisement.

I submit that most of what you and I have been discussing is not particularly relevant to the OP's question.

 

[wwhitney]

Simple example of an install with multiple 705.12(A) disconnects: 200A meter/main/distribution, (2) 20A feeders for two strings of microinverters supplied by (2) 20A circuit breakers in the combo panel, both located at the opposite end of the bus from the utility supply.

That arrangement complies with 705.12(A); there is no requirement to use a single 40A breaker in the combo panel to supply a combiner panel with (2) 20A breakers.

Cheers, Wayne

P.S. As an aside, if this is a residence, a combo panel is typically outside, so the (2) 20A breakers would count as the Rapid Shutdown Initiation Devices required by 690.12(C). If instead you have an outdoor meter and 200A service disconnect, but no distribution, and the distribution panel and (2) 20A breakers are indoors, then you'd need to do something else. Could you use shunt trip breakers and put a button outside that complies with 690.12(C)(3), and is that a reasonable solution?

 

[jaggedben]

But he is still limited to 32A of total backfeed. (32A)(1.25) + 200A = 240A, which is 120% of the bus rating.

That's not the topic of the thread though.

 

[ggunn]

That's not the topic of the thread though.

Well, OK, but he submitted a drawing that shows a 200A/200A MDP and four backfed string inverters. He may not have a 705.12(A) issue but he almost certainly has one with 705.12(B).

 

[PWDickerson]

Asking this group to stay on point is a big ask! But here is the short and sweet. 2020 NEC 705.12(A) is simply telling us that each inverter output circuit has to land on a dedicated breaker or fuse. That's it.

If you have multiple inverters, you can land each one on a breaker in a combiner panel if you want, and then land the combined circuit in the MSP, but you don't have to do it that way. You can land each one on it's on breaker in the MSP as long as you follow all the other rules. You could even land one inverter on a breaker in the MSP, and another inverter on a breaker in a sub-panel. 705.12(A) does not prohibit this. It just tells us that each inverter has to have its own dedicated breaker or fuse.

 

[jaggedben]

each inverter output circuit has to land on a dedicated breaker or fuse. That's it.

Essentially correct.

It just tells us that each inverter has to have its own dedicated breaker or fuse.

No the way you said it the first time was better. Multiple inverters can share an inverter output circuit where the manufacturer allows.

 

[PWDickerson]

Essentially correct.


No the way you said it the first time was better. Multiple inverters can share an inverter output circuit where the manufacturer allows.

Of course you are correct, but for those of us that don't live, eat, and breathe this stuff every day, each string inverter (like the ones in the OP's attachment) needs to land on its own breaker or set of fuses. Micro-inverters can share an inverter output circuit following the limitations provided by the manufacturer.