UL 3741 and NEC 690.12

[louis hannon]

Based upon the premise that the goal of UL 3741 and NEC 690.12 is to protect Firefighters when a PV system is installed on a roof where they might come into contact with it, what about a scenario where the PV system is installed 20' above the roof on a canopy? My question, is that a "rooftop installation" or a canopy for PV installed on a rooftop. Does that mean 690.12 does not apply? If a canopy for parking cars is also the mounting structure for a PV installation, then 690.12 does not apply because it poses no risk to a Firefighter. Where is the risk if the canopy is 20' above the roof? Thanks in advance for some feedback.

 

[jaggedben]

At the very least 690.12 applies to conductors that leave the array to go in or on the building. But it would also apply to an array that is 'on a building'. Good luck arguing that the canopy is not on a building.

Read the definition of a building on Article 100. A canopy on the ground is arguably not a building, but it's ultimately up to the AHJ to decide.

You can go on about intent all you want but the AHJ is not obligated to consider it, especially if the literal meaning of the code is clear.

 

[pv_n00b]

It's going to be an AHJ call and most AHJs will consider a canopy above a building roof the same as PV on the roof. We fight with AHJs all the time on if a canopy on a parking garage needs RSD. Sometimes even a simple parking lot canopy will have an AHJ say it needs RSD because what if a car catches on fire and the firefighter has to climb on the canopy to put it out?

 

[louis hannon]

At the very least 690.12 applies to conductors that leave the array to go in or on the building. But it would also apply to an array that is 'on a building'. Good luck arguing that the canopy is not on a building.

Read the definition of a building on Article 100. A canopy on the ground is arguably not a building, but it's ultimately up to the AHJ to decide.

You can go on about intent all you want but the AHJ is not obligated to consider it, especially if the literal meaning of the code is clear.

I believe you are on track. The best solution is going to be finding a UL3741 racking system that is approved for this sites wind load at 20' above a 9 story building.

 

[louis hannon]

It's going to be an AHJ call and most AHJs will consider a canopy above a building roof the same as PV on the roof. We fight with AHJs all the time on if a canopy on a parking garage needs RSD. Sometimes even a simple parking lot canopy will have an AHJ say it needs RSD because what if a car catches on fire and the firefighter has to climb on the canopy to put it out?

It will be interesting. 2 out of the 4 acres of PV will be 20' above the parking garages.

 

[wwhitney]

Read the definition of a building on Article 100. A canopy on the ground is arguably not a building

Sorry, what's that argument? The entire canopy is equipment, so it's not a structure?

Cheers, Wayne

 

[don_resqcapt19]

This new exception added to the 2023 code may help.

Exception No. 2:
PV equipment and circuits installed on nonenclosed detached structures including but not limited to parking shade structures, carports, solar trellises, and similar structures shall not be required to comply with 690.12.

 

[jaggedben]

Sorry, what's that argument? The entire canopy is equipment, so it's not a structure?

Cheers, Wayne

The argument is that it's a silly definition.

My wording was off the mark. My point was that, surprising as it may be, an AHJ can indeed totally call a canopy a 'building' under the NEC definition, as you're getting at. How a building is really different from a structure is unclear to me. I think the definition of a building should involve enclosed space or something. But that's not the definition.

 

[jaggedben]

This new exception added to the 2023 code may help.

So 'detached' exempts the parking lot canopy on the ground but not the one on the top level of the multi-story parking garage.

 

[pv_n00b]

It's been a significant pain point in the PV industry getting AHJs to classify PV arrays on parking structures as not needing RSD. People have been bringing this up in code forums for years. The NEC does a poor job of defining a building, and AHJs are typically not comfortable using the description in the real building code to apply to the NEC. The additional wording added as an exception to 690.12 in 2023 was intended to help here. The IN for the exceptions reads;

Exceptions for rapid shutdown are intended to be consistent with building and fire codes that have limitations as to the types of buildings on which firefighters typically perform rooftop operations.

Firefighters do not perform rooftop operations on canopy PV on parking structures, so no RSD should be required.

So 'detached' exempts the parking lot canopy on the ground but not the one on the top level of the multi-story parking garage.

The use of "detached" was to keep the exception from applying to PV canopies that are extensions of a building. If someone had a patio shade structure that was attached to the house it would not get to use the exception. There has to be a gap, however small. But it was intended that "nonenclosed detached structure" would include PV on parking garages that are nonenclosed and not attached to another building. It's still not perfect. Small steps.

 

[wwhitney]

It's been a significant pain point in the PV industry getting AHJs to classify PV arrays on parking structures as not needing RSD.

Because they shouldn't, until possibly the 2023 NEC, based on the definitions.

The NEC does a poor job of defining a building

If by poor you mean imprecise, I disagree. If by poor you mean excessively broad, that's true.

and AHJs are typically not comfortable using the description in the real building code to apply to the NEC.

Nor should they, they should use the definition in the NEC. If it is too broad, either the NFPA needs to amend the model code, or the jurisdiction needs to amend the NEC before adopting it.

Cheers, Wayne

 

[jaggedben]

... If by poor you mean imprecise, I disagree. If by poor you mean excessively broad, that's true.

...

It's terribly imprecise, and not meaningfully different from the definition of 'structure'. (What kind of structure doesn't stand alone?)

I haven't cataloged code requirements that apply to buildings and not structures, and vice versa, and both. But I have to wonder why the NEC has two definitions that are almost the same.

 

[wwhitney]

It's terribly imprecise, and not meaningfully different from the definition of 'structure'. (What kind of structure doesn't stand alone?)

Looking again, I agree the wording is poor, I was just mentally translating it to convey the obvious intended difference. Namely, firewalls can divide a single structure into multiple buildings. That's it, that's the point of there being two different terms.

But I agree the NEC is conflicted in its use of the term building. For example, the 2017 NEC (the last version I have as a searchable PDF) uses the phrase "building or other structure" 33 times: once in 215, mostly in 225 and 230, and a few times in the 690s. That phrase is completely redundant, as every building is part of a structure, and any structure is one or more buildings.

I'm slightly torn as to what PI to submit on the definition of "building". One option is to stick with the current intention and just provide language that actually says what is intended. E.g translate "a connected component of a structure minus its firewalls" from math speak to NEC speak. Or the other option is to try to change the definition to better match what is in the building codes.

Cheers, Wayne

 

[pv_n00b]

Nor should they, they should use the definition in the NEC. If it is too broad, either the NFPA needs to amend the model code, or the jurisdiction needs to amend the NEC before adopting it.

Cheers, Wayne

There is resistance to making the NEC into the building code by trying to pull all the definitions of the buildings into it. And I can understand that. The NEC just needs a better definition. I mean, this is garbage:
Building.
A structure that stands alone or that is separated from adjoining structures by fire walls. (CMP-1)
Structure.
That which is built or constructed, other than equipment. (CMP-1)

I strict reading of this would make the support structure for a ground mounted PV array a building. It's clearly a structure, and a building is a structure that stands alone. So a ground mounted PV array is mounted on a building based on this definition and should have RSD. That's how poor the definitions are.

 

[pv_n00b]

I'm slightly torn as to what PI to submit on the definition of "building". One option is to stick with the current intention and just provide language that actually says what is intended. E.g translate "a connected component of a structure minus its firewalls" from math speak to NEC speak. Or the other option is to try to change the definition to better match what is in the building codes.

Cheers, Wayne

I have been at some code-making committee meetings where a better definition of "building" is discussed, generally with an eye toward excluding parking garages from the definition, and it gets gnarly fast. It's really hard to come up with a simple definition that means anything, which is why the building code has such complex definitions.
The NFPA 1 definition is interesting, but not helpful.

3.3.29* Building.
Any structure used or intended for supporting or sheltering any use or occupancy. [101,2021]

Based on that a canopy covering a trash bin is a building.

 

[wwhitney]

I mean, this is garbage:
Building.
A structure that stands alone or that is separated from adjoining structures by fire walls. (CMP-1)
Structure.
That which is built or constructed, other than equipment. (CMP-1)

That definition of Structure matches the IBC, so it's fine. The definition of Building is what's different. The 2021 IBC definition almost matches the NFPA 1 definition you quoted, except it just uses the phrase "any occupancy," rather than "any use or occupancy." Which excludes your trash-can cover example.

I strict reading of this would make the support structure for a ground mounted PV array a building.

Yes, it is, that's the only logical conclusion, unless the support structure is all equipment. Which if it is purpose-made for supporting a a ground mount array, is plausible, particularly if it has some special listing (like for grounding and bonding). But if it's just a bunch of 2x4s, certainly it's a building under the definitions.

It's clearly a structure, and a building is a structure that stands alone. So a ground mounted PV array is mounted on a building based on this definition and should have RSD.

Not under the 2017 and later NEC, as there is an exception for wiring from ground mount arrays that enters a building whose "sole purpose is to house PV system equipment." Which would certainly apply to the "building" that is the ground mount array's substructure.

That's how poor the definitions are.

The job of the definitions is to be clear and unambiguous, not necessarily to give you the result you want. I think the "Building" definition's intent does that, although the translation of that intent into text is not great.

Sounds to me like your complaint is primarily with the writers of 690.12; they know what the breadth of the NEC definition is, and they could easily have stated that RSD is only required for "buildings supporting an occupancy" if that was the desire.

Cheers, Wayne

 

[jaggedben]

...


The job of the definitions is to be clear and unambiguous, not necessarily to give you the result you want.

I think you have it backwards. The purpose of a definition on the NEC is to bring about a result. That result (generally) is to apply requirements or permissions to certain situations and not others. It is less important that the definition be unambiguous enough to eliminate borderline situations than that it get the intended non-borderline situations correct.

I think the "Building" definition's intent does that, although the translation of that intent into text is not great.

I could be wrong, but it seems to me the only practical import of the NEC definition of 'Building' is to require additional disconnects for fire separated units. Probably I've missed something else. But I'm frankly unconvinced that the definition translates a sensible intent that produces intended results in its usage across the code.

It doesn't help that the NEC definition of building bears little resemblance to the commonly understood meaning. This makes it prone to misuse. As in...

Sounds to me like your complaint is primarily with the writers of 690.12; they know what the breadth of the NEC definition is, and they could easily have stated that RSD is only required for "buildings supporting an occupancy" if that was the desire.

It seems to me the original writers of 690.12 paid no attention to the NEC definition of building. They probably assumed that the definition was something like the commonly understood meaning, and therefore wouldn't encompass ground mount arrays. Why else why even mention buildings at all? This inconsistency is being slowly rectified with code revisions, and the battle is over where they actually meant to draw the line, which is in a totally different place than the existing NEC definition of a building.

In conclusion, it's my opinion that the NEC definition of a building is a failure.

 

[wwhitney]

I think you have it backwards. The purpose of a definition on the NEC is to bring about a result.

I'd say the purpose of a definition is to let the rule writers bring about the desired result more succinctly. So the discussion so far is certainly evidence that the "building" definition has problems.

I could be wrong, but it seems to me the only practical import of the NEC definition of 'Building' is to require additional disconnects for fire separated units.

It means that for example 230.2 permits multiple services to a single structure that is multiple buildings, without any explicit language to that effect.

Of course the NEC doesn't define "fire wall." Are we then to use the colloquial meaning of the term, as in 2 hour fire rated wall, or the IBC definition, which requires that the structures on either side of the fire wall be structurally independent, so that one can burn to the ground without affecting the integrity of the other?

It seems to me the original writers of 690.12 paid no attention to the NEC definition of building.

Then that is the proximate cause. I agree that the poor definition of building is being an impediment to writing the rules correctly, rather than a benefit as it should be.

Cheers, Wayne

 

[don_resqcapt19]

.....
It seems to me the original writers of 690.12 paid no attention to the NEC definition of building. ...

One of the issues is that many of the code making panel members for 690 and related articles have little knowledge of the rest of the NEC, thinking that their articles are completely isolated from the rest of the code.
That is why we almost had a new Article 231, Electric Power Sources Interconnected with an Electric Utility, that would have taken control of pretty much everything that is in Article 705. Article 231 appeared in the First Draft Report for the 2023 code. The correlating committee stepped in and formed a task group of members from panels 4, 5, and 10 and a compromise was worked out for the line side connection issues that panel 4 had been ignoring for a very long time.

 

[pv_n00b]

One of the issues is that many of the code making panel members for 690 and related articles have little knowledge of the rest of the NEC, thinking that their articles are completely isolated from the rest of the code.
That is why we almost had a new Article 231, Electric Power Sources Interconnected with an Electric Utility, that would have taken control of pretty much everything that is in Article 705. Article 231 appeared in the First Draft Report for the 2023 code. The correlating committee stepped in and formed a task group of members from panels 4, 5, and 10 and a compromise was worked out for the line side connection issues that panel 4 had been ignoring for a very long time.

It was pretty sad that the CMPs could not work out their differences without resorting to battling each other using the NEC chapters they controlled. CMP4 was living in a bubble and ignoring everyone else working on the NEC. Solar can be pretty insular and I still run into contractors and engineers working in solar who have a very low level of understanding of the first four chapters of the NEC.