Photovoltaic question

[pv_n00b]

This is one of those weird things in the NEC where they just never bothered to make a distinction. You can have a bare EGC or an insulated EGC. If it's insulated the voltage rating of the insulation needs to match or exceed the highest voltage in the other conductors. Yes, it makes no sense, but that's how it's written. This question comes up fairly regularly and maybe your AHJ won't care, maybe they will. If they won't allow it there is no code substantiation you can use to justify the lower rating of the EGC insulation.
Based on what I hear, almost no AHJs care about this. But there's always that one AHJ hiding out there who does not say anything until the final inspection, and then they get you.

 

[Dennis Alwon]

That's the conventional wisdom, but I'm not sure I buy it. If you run emt as your EGC, and the circuit inside is on a 30A breaker, then if you have a #12 Cu green wire inside, I agree the green wire is not an adequately sized EGC. But that just makes it an extra green wire you felt like having that is bonded at both ends to the EGC; the EMT is still your EGC. What section prohibits that extra green wire?

Cheers, Wayne

That is an argument you can take up with the Code panel. T. 250.122 is the only section that states #10 wire on a 30 amp circuit. That is all we have to go by.

 

[wwhitney]

If it's insulated the voltage rating of the insulation needs to match or exceed the highest voltage in the other conductors.

Sorry, maybe I missed it, but what's the exact code citation?

Cheers, Wayne

 

[wwhitney]

That is an argument you can take up with the Code panel. T. 250.122 is the only section that states #10 wire on a 30 amp circuit. That is all we have to go by.

I don't think I need to take it up with the Code panel. Unambiguously T 250.122 tells us that the #12 green wire in the conduit with the 30A circuit is not an EGC. But is there anything in the NEC that prohibits the installation of a green #12 non-EGC non-circuit conductor in that conduit?

Cheers, Wayne

 

[Dennis Alwon]

Where are you going with this Wayne? Once you hook it up it is an equipment grounding conductor, IMO. I agree the rule is lacking but that is how it is...

The other question is why would one want to do it?

 

[jaggedben]

The other question is why would one want to do it?

It's more that you'd want to be allowed to leave it alone if someone had already done it that way. Which is not an unrealistic scenario.

 

[Dennis Alwon]

It's more that you'd want to be allowed to leave it alone if someone had already done it that way. Which is not an unrealistic scenario.

Just cut it...or don't connect it.

 

[jaggedben]

Just cut it...or don't connect it.

That would be less safe (someone working on it expects it to be bonded) and unnecessary. It would arguably violate the prohibition on using green to identify anything another than a grounding conductor.

The code does not specify what to do with items that are installed unnecessarily. This includes both insulation on EGCs and wire type EGCs that aren't required. I do not agree that an EGC's insulation ever has to meet any specification, because the insulation isn't required at all. I do not agree that a green wire installed where there is another valid EGC is required to be any particular size, because it's size is allowed to be zero.

 

[Another C10]

(someone working on it expects it to be bonded)

remember rule number 1, never assume power is off or that everything is the way its suppose to be.

 

[jaggedben]

remember rule number 1, never assume power is off or that everything is the way its suppose to be.

That is no excuse for making the next guy's job more difficult.

 

[Another C10]

That is no excuse for making the next guy's job more difficult.

Sorry its not an excuse its a precaution any smart electrical type considers when working on electrical systems. Be carful in thinking all systems
are safe and sound, mistakes are made, connections become loose and elements can alter a function.

But I think I know what your saying, If installations are done correct and everything stays the same its should be fine.

 

[pv_n00b]

Sorry, maybe I missed it, but what's the exact code citation?

Cheers, Wayne

110.3(B), 110.4

 

[jaggedben]

110.3(B), 110.4

Did you forget what the question was?

 

[curt swartz]

110.3(B), 110.4

Neither of those require the grounding conductor to have an insulation rating to match the un-grounded conductors.
Even the grounded conductors on MV systems are not required to have over 600 volt insulation and many times can be bare.

 

[Another C10]

so ... 54 posts later and many folks aren't in much of an agreement it seems, I've glanced over the conversation and it seems in a nut shell the question was which insulation rating for a rack ground wire be, 1000v rated insulation or 600v rating which apparently both conditions exist within the cable tray. For any questions or for the purpose of accommodating Mr. Inspector, I'd say the 1000v rating would eliminate any arguable violation.

As far as Grounding wire needing Insulation, I cant imagine the importance of such a requirement other than the green color makes it obvious of its intention, the down side of insulating the grounded wire could mean that there is actually less surface area of grounding within the intended grounding path, relying solely on the stripped ends where it terminates.

The upside of a ground with green insulation is as mentioned its obvious identity and also the protection of the ground wires surface entirety from oxidation.

Grounds in Romex or NM cable is bare, Bare Armor Ground is bare inside the protective shield.

My argument would be that having a voltage rating on an insulated green wire is pretty nutty, remember the purpose of a voltage rating on insulation is more so intended for steady voltage use so as to not over heat the insulation causing it to breakdown.

A ground wires purpose is to send any fault current of the applied voltage if present back to the thermal breaker of origin and usually within 30 seconds that breaker trips. Therefore the need to provide a 600v /1000v insulation rating to a conductor that is only energized for roughly 30 seconds is pretty silly.

Just a thought ..

 

[ggunn]

so ... 54 posts later and many folks aren't in much of an agreement it seems, I've glanced over the conversation and it seems in a nut shell the question was which insulation rating for a rack ground wire be, 1000v rated insulation or 600v rating which apparently both conditions exist within the cable tray. For any questions or for the purpose of accommodating Mr. Inspector, I'd say the 1000v rating would eliminate any arguable violation.

As far as Grounding wire needing Insulation, I cant imagine the importance of such a requirement other than the green color makes it obvious of its intention, the down side of insulating the grounded wire could mean that there is actually less surface area of grounding within the intended grounding path, relying solely on the stripped ends where it terminates.

The upside of a ground with green insulation is as mentioned its obvious identity and also the protection of the ground wires surface entirety from oxidation.

Grounds in Romex or NM cable is bare, Bare Armor Ground is bare inside the protective shield.

My argument would be that having a voltage rating on an insulated green wire is pretty nutty, remember the purpose of a voltage rating on insulation is more so intended for steady voltage use so as to not over heat the insulation causing it to breakdown.

A ground wires purpose is to send any fault current of the applied voltage if present back to the thermal breaker of origin and usually within 30 seconds that breaker trips. Therefore the need to provide a 600v /1000v insulation rating to a conductor that is only energized for roughly 30 seconds is pretty silly.

Just a thought ..

All I can do is repeat what I said earlier, which is that I have been using THWN-2 ground wires with 1000V and 2000V PV wiring for every 1000VDC commercial PV system I have designed in several jurisdictions all over the country, and I have never been challenged on it.

 

[pv_n00b]

Did you forget what the question was?

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.

 

[pv_n00b]

Neither of those require the grounding conductor to have an insulation rating to match the un-grounded conductors.
Even the grounded conductors on MV systems are not required to have over 600 volt insulation and many times can be bare.

If the conductor is listed and labeled for a specific maximum voltage then it shall match the voltage of the circuit. If the EGC is protecting a 480V circuit the insulation needs to be at least 480V. The NEC fails to make an exception for EGC conductors. I think it's dumb and I'm not defending the code, but it is what the code requires. There is no alternate reading or interpretation.

Equipment that is listed, labeled, or both shall be installed and used in accordance with any instructions included in the listing or labeling.

Throughout this Code, the voltage considered shall be that at which the circuit operates. The voltage rating of electrical equipment shall not be less than the nominal voltage of a circuit to which it is connected.

 

[petersonra]

If the conductor is listed and labeled for a specific maximum voltage then it shall match the voltage of the circuit. If the EGC is protecting a 480V circuit the insulation needs to be at least 480V. I think it's dumb and I'm not defending the code, but it is what the code requires. There is no alternate reading or interpretation.

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

 

[pv_n00b]

All I can do is repeat what I said earlier, which is that I have been using THWN-2 ground wires with 1000V and 2000V PV wiring for every 1000VDC commercial PV system I have designed in several jurisdictions all over the country, and I have never been challenged on it.

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.