NEC 690.12 - RSID's for Solar Carport with Inverter AC Output Conductors Run Over a Building to Electrical Room - What Solution will Satisfy 690.12?

[PV Designer]

Solar carports are generally considered ground mounts, and not subject to the rapid shutdown requirements of NEC 690.12.

However, consider a carport with inverters mounted on its columns, the inverters are combined in a panel at the carport. The combined AC output conductors are then run underground to a nearby building, run up the exterior wall, over the rooftop, and down the opposite wall, to interconnect with the facility's main distribution panel in the the electrical room on the opposite side of the building from where the carport is located.

The rapid shutdown requirements of 690.12 clearly apply to the inverter AC output conductors on the building. However, the question is whether the AHJ will accept the AC disconnect as a sufficient RSID, since only the AC conductors are in question here. My reading of 2020 NEC 690.12(C) and (D) suggests that the AC disconnect in the interior electrical room where the utility meter and disconnect are located is a sufficiently code compliant, safe and effective RSID for the conductors in question, satisfying both the intention and the letter of the code.

My concern is that the AHJ may require RSID's on the DC side of the system, because these are specifically "listed" as RSID's.

What are your thoughts on this? Do you have any experience with similar situations? Obviously, I will not quote you in any legal disputes, but I am curious to know if my thinking is off, or on target. What do you think?

 

[ggunn]

My opinion: If the inverters are not in or on the building, then you are covered.

 

[wwhitney]

A few comments, just based on the text of 2020 NEC 690.12, no opinion or knowledge of how AHJs will interpret it:

1) It seems to me that a "solar carport" is arguably a building and requires RSD. A ground mount array is arguably not a building (under the expansive NEC definition thereof), as it's all equipment. But once you elevate the array you are adding structural members that service a different purpose beyond the electrical installation, namely to support the use as a carport. I could go either way on this point, maybe elevating the array only involves lengthening and enlarging structural members.

2) Why not move the inverter(s) to be just outside the array boundary? Then there are no 690.12(A)(2) conductors, and the only controlled conductors are the PV system DC circuits.

3) Even when do you have the inverters within the array boundary, so that the "inverter output circuits" are controlled conductors, doesn't that circuit end at the PV system disconnect? In which case you could just locate the PV system disconnect away from the non-carport building, so that the conductors on that building are not inverter output circuits.

Cheers, Wayne

 

[PV Designer]

H

A few comments, just based on the text of 2020 NEC 690.12, no opinion or knowledge of how AHJs will interpret it:

1) It seems to me that a "solar carport" is arguably a building and requires RSD. A ground mount array is arguably not a building (under the expansive NEC definition thereof), as it's all equipment. But once you elevate the array you are adding structural members that service a different purpose beyond the electrical installation, namely to support the use as a carport. I could go either way on this point, maybe elevating the array only involves lengthening and enlarging structural members.

2) Why not move the inverter(s) to be just outside the array boundary? Then there are no 690.12(A)(2) conductors, and the only controlled conductors are the PV system DC circuits.

3) Even when do you have the inverters within the array boundary, so that the "inverter output circuits" are controlled conductors, doesn't that circuit end at the PV system disconnect? In which case you could just locate the PV system disconnect away from the non-carport building, so that the conductors on that building are not inverter output circuits.

Cheers, Wayne

Hi, Wayne.

1) Thank you for your well-thought-out response. Experience shows that most AHJ's will consider carports as ground mounts, rather than structures, although that is a bit of a grey area, where an AHJ could reasonably argue as you have suggested.

2) Moving the inverters outside the array boundary to escape 690.12(A)(2) is a great idea. Now I need to evaluate the space availability and cost difference between a separate fenced off inverter area versus adding RSID's to the system.

3) I like your thinking on isolating the "inverter output circuit", however, I believe these circuits may be interpreted to include all conductors back to the point of interconnection. However, if the circuits from the inverter combiner panel to the AC disconnect and POI may not be considered "inverter output circuits", depending on the AHJ.


I really appreciate your feedback. Thank you,
Isaac

 

[ggunn]

A few comments, just based on the text of 2020 NEC 690.12, no opinion or knowledge of how AHJs will interpret it:

1) It seems to me that a "solar carport" is arguably a building and requires RSD. A ground mount array is arguably not a building (under the expansive NEC definition thereof), as it's all equipment. But once you elevate the array you are adding structural members that service a different purpose beyond the electrical installation, namely to support the use as a carport. I could go either way on this point, maybe elevating the array only involves lengthening and enlarging structural members.

2) Why not move the inverter(s) to be just outside the array boundary? Then there are no 690.12(A)(2) conductors, and the only controlled conductors are the PV system DC circuits.

3) Even when do you have the inverters within the array boundary, so that the "inverter output circuits" are controlled conductors, doesn't that circuit end at the PV system disconnect? In which case you could just locate the PV system disconnect away from the non-carport building, so that the conductors on that building are not inverter output circuits.

Cheers, Wayne

690.12 does not apply. A carport structure without enclosing walls is not a building and does not invoke rapid shutdown requirements. I went to a NABCEP sanctioned educational seminar yesterday where this was covered; the discussion leader pulled up a section of the 2023 NEC that showed this unambiguously. I do not remember where it is, but I will look for it.

Moreover, I have designed several of these things without RSID and I have never been challenged by an AHJ on this point.

What about a solar shade over the top floor of a parking garage? Hmmmm... That could go either way; best have a meeting with your AHJ about that one.

 

[wwhitney]

A carport structure without enclosing walls is not a building

False under the NEC, so let's stop right there. The NEC has a weird definition of "building" that includes any structure. Enclosing walls or not has nothing to do with it.

Cheers, Wayne

 

[PV Designer]

A carport structure without enclosing walls is not a building and does not invoke rapid shutdown requirements. I went to a NABCEP sanctioned educational seminar yesterday where this was covered; the discussion leader pulled up a section of the 2023 NEC that showed this unambiguously. I do not remember where it is, but I will look for it.

Moreover, I have designed several of these things without RSID and I have never been challenged by an AHJ on this point.

A solar shade over the top floor of a parking garage? Hmmmm... Best have a meeting with your AHJ about that one.

Hey, thank you for your input here. When I read 2023 NEC 690.12 of the 2023 NEC, it seems the rapid shutdown requirements on carports depends on one's interpretations of the terms "Building", "Structure" and "Equipment" in Article 100 of the NEC. I'd love to discover a definitive code section!

 

[PV Designer]

False under the NEC, so let's stop right there. The NEC has a weird definition of "building" that includes any structure. Enclosing walls or not has nothing to do with it.

Cheers, Wayne

Agreed. It depends on how one interprets the NEC definitions of Building, Structure, and Equipment in the Article 100.

 

[PV Designer]

Hey, thank you for your input here. When I read 2023 NEC 690.12 of the 2023 NEC, it seems the rapid shutdown requirements on carports depends on one's interpretations of the terms "Building", "Structure" and "Equipment" in Article 100 of the NEC. I'd love to discover a definitive code section!

The challenge here is that the inverter AC output conductors are run up and over a building as the most cost effective way to get to the electrical room. So these particular conductors seem to be subject to rapid shutdown requirements, which makes sense. But I'm thinking a simple AC disconnect would suffice.

 

[ggunn]

False under the NEC, so let's stop right there. The NEC has a weird definition of "building" that includes any structure. Enclosing walls or not has nothing to do with it.

Cheers, Wayne

Stop if you want but that is incorrect. As I said, I have experience with designing solar parking shades, and RSID has not once been an issue, even with difficult AHJs who are real sticklers for code compliance. Some common sense must come into play here; rapid shutdown is to protect firefighters who are on a rooftop chopping holes to ventilate a building. That would never be necessary on a shade structure that is open on the sides and with modules exposed from the bottom.

The language that supports this may be an exception; as I said, I will look for it.

 

[PV Designer]

Stop if you want but that is incorrect. As I said, I have experience with designing solar parking shades, and RSID has not once been an issue, even with AHJs who are real sticklers for code compliance.

I appreciate your experience, and do believe that most AHJ's will be reasonable, and not consider a carport a building. However, 1) I stand by my previous statement that whether or not a carport is considered a building by any given AHJ depends on their interpretation of the definitions of the words Building, Structure and Equipment in NEC Article 100, and B) this is all irrelevant to the question I asked, which is about AC conductors of a carport running up, over and down a building to the electrical room, which have a greater possibility of being subject to rapid shutdown requirements.

 

[ggunn]

The challenge here is that the inverter AC output conductors are run up and over a building as the most cost effective way to get to the electrical room. So these particular conductors seem to be subject to rapid shutdown requirements, which makes sense. But I'm thinking a simple AC disconnect would suffice.

They aren't but if they were, a disco would do it.

 

[ggunn]

Stop if you want but that is incorrect. As I said, I have experience with designing solar parking shades, and RSID has not once been an issue, even with difficult AHJs who are real sticklers for code compliance. Some common sense must come into play here; rapid shutdown is to protect firefighters who are on a rooftop chopping holes to ventilate a building. That would never be necessary on a shade structure that is open on the sides and with modules exposed from the bottom.

The language that supports this may be an exception; as I said, I will look for it.

Got it. It's 690.12 Exception No. 2 in the 2023 NEC.

 

[wwhitney]

Got it. It's 690.12 Exception No. 2 in the 2023 NEC.

Great. The presence of the exception in the 2023 NEC recognizes that a carport is a building, which is why the exception is necessary.

Unfortunately for the OP, CA has not adopted the 2023 NEC yet (I think it will be adopted on January 1, 2026). Although appealing to the allowances of the 2023 NEC might work with the AHJ, could be worth a try.

Cheers, Wayne

 

[ggunn]

Great. The presence of the exception in the 2023 NEC recognizes that a carport is a building, which is why the exception is necessary.

Unfortunately for the OP, CA has not adopted the 2023 NEC yet (I think it will be adopted on January 1, 2026). Although appealing to the allowances of the 2023 NEC might work with the AHJ, could be worth a try.

Cheers, Wayne

OK, since we are splitting hairs...

The exception does not say that a carport is a building; it refers to "parking shade structures, carports, solar trellises and other similar structures" as structures; the word "building" does not appear anywhere in the verbiage.

Also, the discussion leader I referred to, who is an internationally recognized authority on renewable energy systems, someone with whom I have had a professional relationship for several years, and a person whose privacy I will respect by not mentioning his name (but his last name rhymes with "bayfield") referred to this exception added to the 2023 NEC as "not a change but a clarification".

But have it your way; I don't care, but in my opinion for the OP to design this project to conform with rapid shutdown requirements would be an unnecessary expenditure of time, effort, and money. And of course, as always, he should run it by the AHJ before building it; as we all know all too well there is the occasional clueless AHJ out there.

 

[ggunn]

BTW, I have designed 50 or 60 of these things, all without rapid shutdown, and it never came up in any plan review.

Something that just occurred to me is that the AHJ will probably want a PV AC disconnect on the outside of the building and quite possibly another one n the electrical room.

 

[wwhitney]

The exception does not say that a carport is a building; it refers to "parking shade structures, carports, solar trellises and other similar structures" as structures; the word "building" does not appear anywhere in the verbiage.

Yes, but the exception is appropriate because of the (silly) NEC definition of building.

Also, the discussion leader I referred to, who is an internationally recognized authority on renewable energy systems, someone with whom I have had a professional relationship for several years, and a person whose privacy I will respect by not mentioning his name (but his last name rhymes with "bayfield") referred to this exception added to the 2023 NEC as "not a change but a clarification".

Maybe we can agree on this formulation: the CMP writing Article 690 was using the word "building" in the conventional sense, rather than in accordance with the NEC definition, and the exception was added to clarify their intention and bring the text in accordance with the NEC definition.

Cheers, Wayne

 

[jaggedben]

Notwithstanding the NECs crapulent definition of a building, I've not met any AHJ who would actually follow Wayne's argument. Hopefully the 2023 exception will sway anyone who has reservations.

 

[ggunn]

Maybe we can agree on this formulation: the CMP writing Article 690 was using the word "building" in the conventional sense, rather than in accordance with the NEC definition, and the exception was added to clarify their intention and bring the text in accordance with the NEC definition.

Well, OK, but I have never once run into an AHJ who classed a parking shade as a building, and as I said, I have designed a lot of these things in several jurisdictions. IMO, one needs to look beyond the vagueness and ambiguity in some parts of the NEC to grasp what the some of the articles are actually struggling to say. This one is pretty obvious; a solar parking shade is far more like a ground mount than anything that is obviously a building.

There are limitations that are locally enforced, of course. In Houston, TX, there is an upper limit on the square footage of a solar parking shade; I once had to amend my design by splitting the structures into smaller shades to comply. Likewise, in a jurisdiction in California I had to do something similar because shades of over a certain size had to have firewalls and sprinklers.

 

[wwhitney]

IMO, one needs to look beyond the vagueness and ambiguity in some parts of the NEC

I'm more or less with you on your comments except on this point as it relates to 690.12. There's nothing vague or ambiguous about the definition of "building" in the NEC.

The issue is just that the definition doesn't match the (presumed) expectations the writers of 690.12 had, nor the expectations of the AHJs applying 690.12. So that's fine, they can collectively decide that the definition is wrong, or 690.12 is written wrong given the definition, and apply their collective judgement to enforce a more reasonable rule. Or perhaps most often, never even look at the NEC definition of "building" and just use the definition they're used to.

Basically this is just a case of everyone collectively agreeing (perhaps unknowingly) to ignore Charlie's rule. Until someone made a PI for the 2023 NEC for 690.12 that says (I'm guessing, I didn't read it) "hey this doesn't actually say what we've all been thinking it says, so maybe we should fix that."

Given all that, I would say that you're correct in your advice to the OP to just assert in the permit application that the carport is not a building and so 690.12 doesn't apply. And then only if the AHJ pushes back, look to convince them in fact it's not a building because the support structure is all equipment, or to allow the use of not-yet-adopted 690.12 Exception 2, or move the inverter outside the footprint of the carport, or whatever.

Cheers, Wayne