Art 250 with lighting on PV Carport

[SteveO NE]

I am wondering what the general consensus is with the following circles I've seen discussions go regarding this with Electricians, AHJs, and Engineers. Aux grounding electrode, or EGC is adequate? I am currently a fly on the wall between 3 parties arguing this (and I'm staying out of it for now) but its not the first time I've seen it come up so I was curious what others thought of this.

690.47 - This seems debated amongst people in my area but this says the EGC is adequate for bonding a detached carport structure (Steel/conductive). The debate as compared to a ground mount is that it is providing a separate covered structure for parking. Feel free to weigh into that.

250.32 (A) - Separate building, separate electrode. Goes to the point of the structure providing covered parking. It gives an exemption of a single branch circuit so lets clarify we aren't talking about that.

Scenario 1: Multiple Inverters with a combiner Panel

Scenario 2: Single or Multiple Inverters but with another single circuit serving lights affixed to the carport. This one seems to get people going. I've heard two arguments here: the lighting circuit further supports the concept that this is a separate functional building beyond just a "PV support structure." I have also heard that if the lighting is a single branch circuit, then it meets the exemption in 250.32 (A) and the PV doesn't count as a branch circuit.

In both scenarios we can assume its fed by a separately derived source because typically we are stepping up, but it would be behind an OCPD at the origination of the feeder (in the primary building structure) side so it shouldn't be a factor really.

Finally, regardless of what the code says, what do you think is best practice? Aux rod or not?

 

[wwhitney]

690.47 starts off "(A) Buildings or Structures Supporting a PV System. A building or structure(s) supporting a PV system shall utilize a grounding electrode system installed in accordance with Part III of Article 250."

Part III of Article 250 starts off with "250.50 Grounding Electrode System. All grounding electrodes as described in 250.52(A)( l ) through (A)(7) that are present at each building or structure served shall be bonded together to form the grounding electrode system."

So a GES "installed in accordance with Part III of Article 250" will be comprised of "electrodes . . . present at . . . [the] building or structure." That means you have to install grounding electrodes at the PV support structure to form a GES to comply with 690.47, and you may not rely on a remote GES to satisfy 690.47.

Cheers, Wayne

 

[ggunn]

690.47 starts off "(A) Buildings or Structures Supporting a PV System. A building or structure(s) supporting a PV system shall utilize a grounding electrode system installed in accordance with Part III of Article 250."

Part III of Article 250 starts off with "250.50 Grounding Electrode System. All grounding electrodes as described in 250.52(A)( l ) through (A)(7) that are present at each building or structure served shall be bonded together to form the grounding electrode system."

So a GES "installed in accordance with Part III of Article 250" will be comprised of "electrodes . . . present at . . . [the] building or structure." That means you have to install grounding electrodes at the PV support structure to form a GES to comply with 690.47, and you may not rely on a remote GES to satisfy 690.47.

Cheers, Wayne

Would the structural steel encased in concrete qualify as a GE?

 

[jaggedben]

I am wondering what the general consensus is with the following circles I've seen discussions go regarding this with Electricians, AHJs, and Engineers. Aux grounding electrode, or EGC is adequate? I am currently a fly on the wall between 3 parties arguing this (and I'm staying out of it for now) but its not the first time I've seen it come up so I was curious what others thought of this.

690.47 - This seems debated amongst people in my area but this says the EGC is adequate for bonding a detached carport structure (Steel/conductive). The debate as compared to a ground mount is that it is providing a separate covered structure for parking. Feel free to weigh into that.

Makes no difference. A groundmount rack is also a structure, read the definition in Article 100. Unclear if a carport is a building.

250.32 (A) - Separate building, separate electrode. Goes to the point of the structure providing covered parking. It gives an exemption of a single branch circuit so lets clarify we aren't talking about that.

Scenario 1: Multiple Inverters with a combiner Panel

Scenario 2: Single or Multiple Inverters but with another single circuit serving lights affixed to the carport. This one seems to get people going. I've heard two arguments here: the lighting circuit further supports the concept that this is a separate functional building beyond just a "PV support structure." I have also heard that if the lighting is a single branch circuit, then it meets the exemption in 250.32 (A) and the PV doesn't count as a branch circuit.

Makes no difference. It also makes no difference if I give you Scenario 3: single inverter, single lighting circuit. In all scenarios you either have a feeder or multiple branch circuits (however you want to argue which the inverter circuit is).

Anyway 690.47 trumps all that. So, if you had a single inverter circuit, maybe you could try to invoke the exception, except you can't anyway.

In both scenarios we can assume its fed by a separately derived source because typically we are stepping up, but it would be behind an OCPD at the origination of the feeder (in the primary building structure) side so it shouldn't be a factor really.

Makes little or no difference. If the transformer is at the carport you have some additional grounding work for it at the carport, and if it's somewhere else you have those requirements at that somewhere else location. There's an exception for running an EGC that could apply if you have a separately derived system grounded remotely and are bringing the grounded conductor to the carport, that's the most 'interesting' situation I can think of. But still a GES at the carport would certainly be required then, as in all scenarios.

Finally, regardless of what the code says, what do you think is best practice? Aux rod or not?

Never "auxilliary" rods, they do next to nothing IMO. Rods if the NEC requires them because you don't have any other NEC compliant electrode. See ggunn's question. Perhaps a more serious electrode system (Ufer? ground ring?) if pouring enough concrete or if an engineer with lightning protection credentials or experience recommends it for that purpose.

 

[jaggedben]

690.47 starts off "(A) Buildings or Structures Supporting a PV System. A building or structure(s) supporting a PV system shall utilize a grounding electrode system installed in accordance with Part III of Article 250."

Part III of Article 250 starts off with "250.50 Grounding Electrode System. All grounding electrodes as described in 250.52(A)( l ) through (A)(7) that are present at each building or structure served shall be bonded together to form the grounding electrode system."

So a GES "installed in accordance with Part III of Article 250" will be comprised of "electrodes . . . present at . . . [the] building or structure." That means you have to install grounding electrodes at the PV support structure to form a GES to comply with 690.47, and you may not rely on a remote GES to satisfy 690.47.

Cheers, Wayne

The interesting thing, as we discussed in another thread a while back, is that the NEC doesn't quite come out and say that the PV system EGC has to be connected to the building or structure GES at the same building. In that other thread the scenario involved a PV array fed from a different service than the regular service to the same building, and I recall we determined that the grounding would be best kept separate. But none of this applies to the OP's scenarios, as far as I can tell.

 

[wwhitney]

The interesting thing, as we discussed in another thread a while back, is that the NEC doesn't quite come out and say that the PV system EGC has to be connected to the building or structure GES at the same building.

That's right, I was glossing over that point in my answer. What 690.47 says is to see Part III of Article 250, and what 250.30 says is "present at each building or structure served."

So if you want to say that the PV system doesn't serve the ground-mount array structure, but instead serves some other building, that would be an argument for using the remote GES on that other building, and 690.47 goes on to say the EGC in the feeder to the ground-mount array is sufficient connection to that. But all an AHJ has to say is "no, the PV system is serving the ground-mount array structure as well," and now you have to have a GES at the ground-mount array.

I think the intent of 690.47 is likely that the structure supporting the PV system have a GES, and so it really should just say "at the building or structure(s)" to nail that down.

Cheers, Wayne

 

[SteveO NE]

So a GES "installed in accordance with Part III of Article 250" will be comprised of "electrodes . . . present at . . . [the] building or structure." That means you have to install grounding electrodes at the PV support structure to form a GES to comply with 690.47, and you may not rely on a remote GES to satisfy 690.47.

To be clear I completely agree. This argument that I hear being made is that it is required to utilized a grounding electrode system that is compliant with Art 250, and then they state an EGC is connected to a compliant system. They are saying that 690.47(B) states its optional, but I read that as its optional to add extra ground protection beyond the GES for the structure and a strange interpretation otherwise, and they then use 690.47(A)(1) to try and justify using the EGC - Believe it or not though, I have seen inspectors saying this is the way it should be done but in my eyes that just means the PV system complies, it doesn't mean the structure complies with Part III 250.

I just wanted to make sure I wasn't going crazy here. In this particular case the customer rightfully wants this and the EOR and inspector are saying its unnecessary. I will step in eventually when I'm asked to but its not my fight yet, I'm the engineer for another party involved in this project ensuring there are extra cooks in the kitchen of course for exactly these types of arguments to take place.

Would the structural steel encased in concrete qualify as a GE?

250.52 (A)(2): Metal In-Ground Support Structures.

...in-ground support structure(s) in direct contact with earth vertically for 3.0m (10ft) or more, with or without concrete encasement...

So I think that one is pretty clear and usually resolves it anyway, it just needs to have the GEC actually bonded to the structural steel at that point.

 

[jaggedben]

You must be looking at the 2023 version, which frankly is all messed up. In 2017 and 2020 it was clear; (A) was requirements, (B) covered optional electrodes for earth worshippers. I agree that the way they changed it in 2023 was hairbrained and creates confusion. FWIW, in the first draft of the 2026 NEC, (B) is just deleted.

 

[pv_n00b]

The NEC does a poor job defining what a "structure" and "building" are. It's always been a problem for PV. Based on a strict reading of the NEC a ground mounted PV array is a structure and every row should have its own GES. But we don't do that, we bond the rows together with EGC and to the inverter with an EGC and it's connected to the GES the inverter uses. Some people put aux electrodes in the array but those are not part of a GES and are just pounding cash into the ground. I would not build a separate GES for a carport, I would bond it to the existing building GES with an EGC to the POI.
If I put a flagpole with a light in my front yard the NEC says that's a structure, who would build a GES for that?

 

[jaggedben]

...
If I put a flagpole with a light in my front yard the NEC says that's a structure, who would build a GES for that?

Public works engineers, or so I gather from the forum. But your example seems to be describing a structure supplied by a single branch circuit, which is different from the OPs scenarios as far as the NEC is concerned.

 

[wwhitney]

The NEC does a poor job defining what a "structure" and "building" are.

Poor perhaps as in overly broad, but the definitions are simple enough and clear enough.

It's always been a problem for PV. Based on a strict reading of the NEC a ground mounted PV array is a structure and every row should have its own GES.

Can't you argue that the entire support structure for a ground mount array is "equipment" (it exists only to support the panels) and so the PV array is not a structure? That would also mean that 690.47 doesn't apply to a ground mount array.

But that doesn't effect the OP, as the carport has an additional function and is clearly a structure.

I would not build a separate GES for a carport

Depends on whether it is attached or detached, somehow I inferred from the OP that it is detached, so my comments have been based on that assumption.

Cheers, Wayne

 

[jaggedben]

Poor perhaps as in overly broad, but the definitions are simple enough and clear enough.
...

No, it's really a problem when the definition of "building" is so far from the dictionary definition and common meaning (i.e that it has a roof and walls). Since very few people (including electricians and inspectors) know the NEC definition and even fewer compute it logically (like you do), it means that essentially no person's first interpretation of whether something is a 'building' stands up to close scrutiny in borderline cases, and arguments can't be settled. No less so because in pertinent cases (e.g. 690.12) is it bleedingly obvious that the code making panel itself didn't know or understand the implications of the NEC definition, and used the word according to its common meaning.

That's what makes the NEC definition of building poor.

(The definition of "structure" is fine, IMO.)

 

[wwhitney]

No less so because in pertinent cases (e.g. 690.12) is it bleedingly obvious that the code making panel itself didn't know or understand the implications of the NEC definition, and used the word according to its common meaning.

What's your basis for this statement? Has anyone submitted a PI to, say, change "buildings" in 690.12 to "enclosed buildings," with the CMP rejecting that on the (incorrect) basis that buildings are already enclosed?

Cheers, Wayne

 

[jaggedben]

What's your basis for this statement? Has anyone submitted a PI to, say, change "buildings" in 690.12 to "enclosed buildings," with the CMP rejecting that on the (incorrect) basis that buildings are already enclosed?

The motivation for 690.12 was to asuage fire departments that had stated they wouldn't fight fires on buildings with rooftop solar. @don_resqcapt19 has talked about it here. The concern was that fire department policies would hurt the rooftop solar industry. It was never about groundmounts or carports.

 

[jaggedben]

What's your basis for this statement? Has anyone submitted a PI to, say, change "buildings" in 690.12 to "enclosed buildings," with the CMP rejecting that on the (incorrect) basis that buildings are already enclosed?

Also Exception no 2 to 690.12 in the 2023 NEC ('non-enclosed') is essentially exactly the example you're looking for. And wouldn't have been necessary if the NEC definition of 'building' resembled the common usage.

 

[wwhitney]

Also Exception no 2 to 690.12 in the 2023 NEC ('non-enclosed') is essentially exactly the example you're looking for.

OK, so that shows that the CMP behind Article 690 understands the weirdness of the NEC definition of "building." (At least they do now, given that they added the exception. I find it a little hard to believe that the application of 690.12 to non-enclosed buildings was unintentional between the time when 690.12 was first adopted and the time when the exception appeared, but maybe so.)

And wouldn't have been necessary if the NEC definition of 'building' resembled the common usage.

Yes, we can change definitions to avoid needing exceptions in the rules that used those definitions.

I don't think any of this really speaks to your main point, which is that the NEC definition of "building" is weird and contrary to standard usage. Which I agree with.

It's still clear enough and simple enough, just not standard enough. : - )

Cheers, Wayne