240.21(C)(2) & (3) with PV

[SteveO NE]

In light of the other thread that just popped up discussing transformers I thought I'd put this out there for discussion as well because I have seen interpretations both ways.

Do you consider PV an industrial installation as it pertains to 240.21(C)? Is there any overarching definition I am missing, not specifically designated to another section of the code (for instance 240.2 specifically states its applicable to Part VII meaning it is not applicable to other parts) that would preclude this? Power generation is considered an industrial application, and (C)(3) does not refer to the facility itself (whereas again 240.2 specifically does), just "the installation", so presuming there are no loads on the transformer other than power generation and station service associated with that power generation, would you, or would you not allow those conductors to be 25' presuming you also meet the 4 conditions outlined. Notwithstanding art 408, and protection of the panelboard itself, this also allows the conductor to be protected by the sum of the breakers in an MLO vs a single OCPD.

 

[pv_n00b]

In general we avoid needing to depend on a PV or BESS installation qualifying for any industrial allowances. Since the NEC pretty much leaves it up to AHJs to define what "industrial" is it can vary by location. A big pain. That being said, it can be more likely to be considered industrial depending on a few things.

• Is the installation site already an obvious industrial site? If I am putting a PV system on an industrial facility that manufacturers something like automobile body panels then it's highly likely I can get an industrial designation to stick to the PV system too
• How big is the PV system? I can probably get AHJ agreement on an industrial designation for a 100MW ground mount PV plant than a 50kW BTM PV on a gym roof

There are tasty industrial allowances for cable tray and conductor protection if you can get the AHJ to go along. This is one of those ask for permission and not ask for forgiveness situations.

 

[SteveO NE]

There are tasty industrial allowances for cable tray and conductor protection if you can get the AHJ to go along. This is one of those ask for permission and not ask for forgiveness situations.

Ah but that's my point:

392.10 (B): In Industrial Establishments

It is clearly denoting that exemption is for the facility itself, whereas 240.21(C) is clearly identifying the installation itself separate from the facility. This seems to be repeated in the code. So that's really the point of the question...does the site matter, because PV generation in and of itself is an industrial system. Honestly as far as AHJ buy in is concerned I don't think I've ever seen this come up with an AHJ, except in the context of the other active thread here regarding primary/secondary protection where I have had an AHJ force me to protect a conductor from both ends (once from the transformer and again from the PV sourcing it) maybe 15 years ago, but that's a whole different mess. I have merely seen this debated amongst colleagues and electricians.

Additionally, one could also argue that your reference does support the point I made above because the PV has the allowance for cable trays per 690.31(C)(2) (2023 and I'm pretty sure I got that right don't have it in front of me to double check) in outdoor locations. One could connect the dots that any outdoor PV locations are required to intend access to only qualified personnel, which is also the requirement of 240.21(C)(3).

All of that said, yes, I am in the same camp, I am personally willing to sign off on the 25' allowance in a bind, based on the justification I posed, but I don't design it that way to intentionally avoid risk of interpretations and senseless arguments post construction. So, I was more asking this from a is there any reason the code shouldn't be interpreted that way as opposed to how should one design it. One of those back pocket arguments to make when someone finds themselves in a bind.

 

[jaggedben]

Yes, the nature of the facility matters. A PV installation is not inherently an industrial installation. This doesn't change because there happens to be a transformer. A PV installation on a commercial office building might use a transformer and this does not mean it's an industrial facility.

Industrial facilities are not defined in the NEC, even though lots of different articles covering lots of different things besides PV give more lenient permissions for industrial facilities. I assume the AHJ would look to other codes or local zoning designations to determine if a facility has been given that designation. Similar to how the NEC refers to occupancies in some places but does not try to define them.

My guess is that a facility that consisted only of a PV installation would probably qualify, but see above.