12v stand-alone PV system grounding

[kanaka360]

In the 2011 NEC, section 690.41 indicates the section to apply to systems over 50 volts.

It is my understanding that the 2014 NEC no longer includes the 50V cutoff, is that correct?

If so, a stand-alone open/closed sign with 100 watt PV panel and 12 volt battery will need a grounding electrode?

I see the reference to 690.35 and 690.71(G), but still not seeing what I'm looking for related to this specific application.

 

[jaggedben]

I don't think the 50V language changed at all in the 2014 NEC, but I don't have the book with me right now to confirm.

Do you understand that the 50V number applies to whether a system conductor is required to be grounded, and not whether a grounding electrode is required? These are two different things.

 

[kanaka360]

Unless my eyes are deceiving me, there's nothing in 690.41 in the 2014 NEC with regard to the 50V requirement.

Correct me if I'm wrong, but in order for the system conductor to be grounded (connected to earth) it needs to eventually connect to a grounding electrode. Hence, a grounding electrode is required for the conductor to be grounded. Based on what I've read on this forum and elsewhere, people are citing 690.41 (2011) to provide installs without a grounding electrode for this type of system. Based on the 2014 code I'm having trouble finding any similar 50v cutoff, so I'm really just wondering if I'm missing something exempting a 100W, 12V stand-alone PV system.

I can't see where this system is exempt, and I know the contractor is not intending to provide all of the provisions for an ungrounded system, so I intend to tell them that they need to provide a grounding electrode conductor per 250.166, as required by 690.47(b).

 

[jaggedben]

Now that I'm home and have the book in front of me...

Yes, you are right, 690.41 changed. Since ungrounded systems are now very common they did away with covering them through an exception, and simply required all ungrounded systems to meet 690.35.

What you say about a grounded conductor requiring a grounded electrode is absolutely true, but the same is considered true for equipment grounding, so I don't really follow the logic of not needing a grounding electrode just because there's no grounded conductor.

There's one section of the 2014 NEC that I think could be relevant to the setup you describe, which is 690.47(D), exception 1. It says "An array grounding electrode shall not be required where the load served by the array is integral to the array." The system you described sounds like it might fit that bill.

In my opinion, if the system fits that exception, and has no grounded conductor, and could not in any way make electrical contact with a premises wiring system, then a grounding electrode should not be required. It would serve no purpose. Also that seems to be the whole purpose of the exception.

 

[ggunn]

690.47(D), exception 1. It says "An array grounding electrode shall not be required where the load served by the array is integral to the array."

Can you explain to me what that means?

 

[jaggedben]

Can you explain to me what that means?

Well the NEC defines an array as 'a mechanically integrated assembly of modules' and other components such as support structures, trackers, etc.. So to me if the load (light, sign, whatever, possibly including battery) is 'mechanically integrated' with the modules then that fits the bill.

You get to decide what's 'mechanically integrated'. For me it would be if you can't remove the support structure for the load without also removing the support structure for the module, or vice versa.

 

[kanaka360]

There's one section of the 2014 NEC that I think could be relevant to the setup you describe, which is 690.47(D), exception 1. It says "An array grounding electrode shall not be required where the load served by the array is integral to the array." The system you described sounds like it might fit that bill.

Unfortunately this section is talking about the additional auxiliary electrode... Don't even get me started about the requirement for this "Auxiliary electrode" (see what Mike Holt has to say about it, if you're wondering). Anyway, I don't think this exemption applies to the other grounding electrode requirements of 690.47, but it probably should....