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?

[jaggedben]

I've been assuming in this "carport array" that there is no roof underneath the solar panels, and the solar panels are the only "roof". If that's the case, you don't have a carport after removing the panels, you just have some columns and some beams.

If you do have a roof under the panels, then I agree it's a carport, and none of that carport is the array support structure, same as case (3).

Any solar carport could have the solar panels removed and replaced with a different material that makes it just a carport, and often vice versa. And there is nothing in the definition of an array that references having a roof under the modules or not. So if you're going to contend that using solar panels on top of a carport necessarily turns the entire carport structure into an array, then putting solar panels on the roof of an enclosed building - especially using BIPV methods - would also necessarily turn the entire building into an array. But this is an unreasonable outcome, and the mere phrase 'with a support structure' doesn't require you to do this. Nothing in the definition precludes you from distinguishing 'support structure' particular to the array from other support structure, or even the array itself from the support structure so long as it's 'with' one.

A reasonable interpretation (and some sort of interpretation is required) might be that support structure is part of the array if it could serve only the purpose of supporting modules. Then a carport structure that is capable of supporting other material that could provide shade needn't be considered part of the array.

 

[wwhitney]

especially using BIPV methods

I think this is the crux of the issue. A solar carport is effectively BIPV, where the panels are the roof.

So I'm inclined now to say that what matters is whether the panels are sealed to each other like a roof would be, or whether rain is free to drip down between the panels. First case--you have a carport in which the PV modules are integrated into the roof, and there is basically no "array support structure". Second case--you have a glorified ground mount array, and the whole structure is the array support structure.

To put it simply, if it's leaky, it's not a carport.

Basically I can't accept the idea that merely lengthening one or more columns can change whether those columns are part of the array support structure. So unless you'd like to argue that the columns in a ground mount array aren't part of the array support structure (makes me wonder whether that is worth exploring), I need to draw the line elsewhere.

Cheers, Wayne

 

[ggunn]

Again, some common sense should be part of the discussion. Rapid shutdown was brought into the NEC specifically to protect firefighters who are on a roof chopping holes to ventilate the building underneath it. Will such a situation ever arise on the structure being considered? Exception 2 to 690.12 clarifies that the answer is no for a solar parking shade. Descending into the minutiae of the NEC like a lawyer trying to find a technicality supporting reasonable doubt in a court case is a nonproductive exercise. What you call something should never be a reason to build a system one way or another.

As I have said, I have designed many of these things going back into previous code cycles, and I have never encountered an AHJ who tried to hold my feet to the fire to design RSD into the plans. YMMV but that is my experience. I don't mean to be pedantic, but my experience is in the real world.

 

[ggunn]

So I'm inclined now to say that what matters is whether the panels are sealed to each other like a roof would be, or whether rain is free to drip down between the panels. First case--you have a carport in which the PV modules are integrated into the roof, and there is basically no "array support structure". Second case--you have a glorified ground mount array, and the whole structure is the array support structure.

Are you saying that whether rain can leak through between the modules should make any difference to rapid shutdown requirements or lack thereof, or any other rules concerning electrical configuration? If so, I must emphatically disagree.

 

[wwhitney]

Are you saying that whether rain can leak through between the modules should make any difference to rapid shutdown requirements or lack thereof, or any other rules concerning electrical configuration?

Should? No. Maybe does because of the language that was adopted and that we have to deal with? Yes.

Anyway, until we hear about an AHJ that actually says 2020 NEC 690.12 applies to solar carports, maybe we've explored the question enough. You seem to have been fortunate enough not to have to deal with any such AHJs. And the 2023 NEC resolves the question via Exception 2.

Cheers, Wayne

 

[jaggedben]

....

Basically I can't accept the idea that merely lengthening one or more columns can change whether those columns are part of the array support structure. So unless you'd like to argue that the columns in a ground mount array aren't part of the array support structure (makes me wonder whether that is worth exploring), I need to draw the line elsewhere.

I gave you my proposed general interpretation, which is based on whether the support structure serves any other purpose. And the outcome of that interpretation tracks as one would expect for groundmounts vs. carports. But it's moot anyway, since RS is required in neither situation.

 

[ggunn]

You seem to have been fortunate enough not to have to deal with any such AHJs. And the 2023 NEC resolves the question via Exception 2.

I'm not sure how much of it has been due to good fortune. My experience with many of these structures in several jurisdictions has all been the same.

 

[wwhitney]

I gave you my proposed general interpretation, which is based on whether the support structure serves any other purpose.

OK, so maybe I should reconsider my statement that just lengthening columns can't make a difference. After all, the difference between an operable casement window that extends to the floor and a single panel french door is primarily the height of the top of the opening and thus whether people can walk through it.

And the outcome of that interpretation tracks as one would expect for groundmounts vs. carports. But it's moot anyway, since RS is required in neither situation.

Hmm, my latest involvement with the discussion began in reaction to the statement "inverters mounted on the columns are not in the boundary of the array". But of course whether that is true or not is moot if 690.12 doesn't apply.

So the question is (a) is a carport array "ground mounted PV" in the sense of 2017 and 2020 NEC 690.12 Exception and if so (b) does that mean the entire array is exempt under that exception?

Under the 2023 NEC, 690.12 Exception 2 exempts all nonenclosed detached structures from all of 690.12.

Cheers, Wayne