Photovoltaic question

[pv_n00b]

What voltage does the EGC operate at? I would suggest it is zero.

Technically it operates during a fault at the voltage of the protected conductors. But again, it's a dumb requirement for an EGC. People should just stop trying to make the NEC say something it does not and move on.

 

[wwhitney]

If the conductor is listed and labeled for a specific maximum voltage then it shall match the voltage of the circuit.

" . . . to which it is connected." The EGC isn't connected to a circuit, and its operating voltage is 0 volts. During a fault conditions the voltage will be higher, but those are not operating conditions.

I have yet to see any text in the NEC which says that a wire which is allowed to be bare, if it is instead insulated, needs to have a particular minimum voltage rating on that insulation.

Edit: The wording of the second sentence of 300.3(C)(1) is slightly ambiguous, but in context the word "conductors" there should be read as "circuit conductors" as discussed in the first sentence. Otherwise it would, for example, imply that bare EGCs are prohibited in an enclosure containing circuit conductors of different systems.

Cheers, Wayne

 

[jaggedben]

I did not forget what wwhitney's question was, and I answered that. Maybe you should go back and look it up? It's #43.

I asked because I was genuinely baffled by your response, which I couldn't make any sense of.

250.199 permits EGCs to be bare. It is the exception you claim the NEC fails to make in post #58, but there it is. Therefore the insulation is not required, therefore no specification can be required of EGC insulation. The fact that an insulation rating is labeled on the wire does not mean I'm violating any listing if I use it as an EGC for which insulation is not required. Unless you can show me manufacturers instructions which prohibit such a use, I don't think that invoking 110.3 or 110.4 holds any water. 250.119 ought to end the discussion, especially if, as you agree, other conclusions are 'dumb.'

 

[ggunn]

This is the argument from experience, and I hear it a lot. I've been doing it this way for decades and no AHJ has ever said it's wrong so it must be right. But I have to point out that AHJs not enforcing a dumb NEC requirement is not the same as saying that the NEC does not require it. There are a number of requirements that traditionally AHJs overlook in the NEC and they have become ingrained in practice for a good reason. They are dumb NEC requirements but for some reason, no one has been able to get them removed. This insulated EGC voltage requirement is dumb, AHJs traditionally overlook it, but it's still in the NEC.

Be that as it may I see no reason to change what I am doing. There is precedent for this; remember the NEC requirement for a grounding electrode at PV arrays that was not only useless but could be dangerous? In the hundreds of PV systems we installed during the code cycle where it was in force we had precisely one inspector make us install one.

 

[tortuga]

In theory could a insulated 600V EGC could enter 1000V equipment / bus duct / switch-gear and be installed in such a way that it is laying across exposed 1000V parts thats not as obvious as if it were bare?
Or when somone is working on the equipment years later and cant see the printing inadvertently moves the wire so its in contact with energized parts?

 

[jaggedben]

In practice, I don't let EGCs lay across live parts at 240 volts, whether bare or insulated, and I've rarely seen such sloppy workmanship. I think we can expect the same or better of people qualified to work on 1000v installations.

 

[tortuga]

In practice, I don't let EGCs lay across live parts at 240 volts, whether bare or insulated, and I've rarely seen such sloppy workmanship. I think we can expect the same or better of people qualified to work on 1000v installations.

From the workmanship I have seen out there in the world these days I have a more cynical view and I bet the CMP does also.
PV_noob brings up a broader philosophical point about 110.3(B) as soon as a product is listed, its uses become very restricted.