AC and DC conductors

[LarryFine]

If a barrier may divide a box for high and low voltages, why wouldn't it do the same for a wireway?

 

[ggunn]

That's a bad argument...

And that's your opinion; time will tell.

 

[ggunn]

If a barrier may divide a box for high and low voltages, why wouldn't it do the same for a wireway?

690.31(B) includes wireways. What box are you referring to; is that in another code article?

 

[jaggedben]

A barrier designed to separate high and low voltage conductors to comply with 300.3 would provide compliance in this case. A barrier merely designed to provide the physical separation of PV and non-PV conductors per 690 would not.

 

[ggunn]

The AHJ accepted my argument and approved our installation, so....

 

[wwhitney]

I had a long winded analysis of the difference between "if X then Y shall be permitted" and "not Y unless X," which I understand to mean "if not X then not Y."

But then I looked at the 2023 version of 690.31(B). Now the exception has a requirement that mirrors 300.3(C). So by putting that in the exception, and not in the parent text that says "unless separated from other circuits by a barrier or partition", the section is distinguishing the 300.3(C) type requirement and not applying it to the "separated by a barrier or partition" case.

So for the 2023 NEC I agree that 690.31(B) overrules 300.3(C). If that was the intention in the 2020 NEC, I'd say they bumbled the wording.

Cheers, Wayne

 

[wwhitney]

The AHJ accepted my argument and approved our installation, so....

Great! And looks like you were right on the intent, judging by the 2023. I just think the 2020 wording doesn't get there.

Cheers, Wayne

 

[mtnelect]

How do handle the signage requirements, when you have a junction box with a barrier inside.

 

[pv_n00b]

Since it's not specified in the NEC I've seen "barriers" fabricated on-site out of whatever scrap was around. Does that make a UL Listed raceway into two separate raceways? Hardly. I've always thought that a "barrier" should be defined as a manufacturer supplied item and not just cardboard cut to fit.
Now if the barrier was an option from the manufacturer and was part of the listing of the raceway that would be a different evaluation.

 

[ggunn]

Since it's not specified in the NEC I've seen "barriers" fabricated on-site out of whatever scrap was around. Does that make a UL Listed raceway into two separate raceways? Hardly. I've always thought that a "barrier" should be defined as a manufacturer supplied item and not just cardboard cut to fit.
Now if the barrier was an option from the manufacturer and was part of the listing of the raceway that would be a different evaluation.

In our case we constructed insertable barriers out of 1/4" or 3/8" clear polycarbonate and the AHJ accepted it.

 

[ggunn]

Great! And looks like you were right on the intent, judging by the 2023. I just think the 2020 wording doesn't get there.

Cheers, Wayne

There is ambiguity in the NEC? Say it ain't so!

 

[solarken]

I would hope this area gets a review and update in NEC soon. Wanting to use a gutter to keep the wiring safe and neat is a good thing. But then having all this confusion and trouble to meet these unclear requirements, may cause many to just keep using separate conduits, which might result in a messier, less maintainable install, which is not good.
I can't think of a reason why 400VDC optimizer output circuits in the same wireway as 240VAC inverter output circuits and using 600V rated THWN-2 is a safety issue for NEC, even without a barrier. Ditto for residential 600V PV output circuits. 300.3(C) allows this generally, but then 690.31(B) adds the barrier requirement. Doesn't make sense for anything except maybe 1000V or 1500V commercial PV circuits.

 

[don_resqcapt19]

I would hope this area gets a review and update in NEC soon. Wanting to use a gutter to keep the wiring safe and neat is a good thing. But then having all this confusion and trouble to meet these unclear requirements, may cause many to just keep using separate conduits, which might result in a messier, less maintainable install, which is not good.
I can't think of a reason why 400VDC optimizer output circuits in the same wireway as 240VAC inverter output circuits and using 600V rated THWN-2 is a safety issue for NEC, even without a barrier. Ditto for residential 600V PV output circuits. 300.3(C) allows this generally, but then 690.31(B) adds the barrier requirement. Doesn't make sense for anything except maybe 1000V or 1500V commercial PV circuits.

If you have ideas for better language or other changes, the system is open for the submission of Public Inputs to make changes for the 2026 code until September 7th, 2023. You can use the link below to access the system to submit a PI.

submit public input

 

[ggunn]

Doesn't make sense for anything except maybe 1000V or 1500V commercial PV circuits.

FWIW, 1000V DC circuits and 600V THWN-2 are exactly my concern.

 

[jaggedben]

I would hope this area gets a review and update in NEC soon. Wanting to use a gutter to keep the wiring safe and neat is a good thing. But then having all this confusion and trouble to meet these unclear requirements, may cause many to just keep using separate conduits, which might result in a messier, less maintainable install, which is not good.
I can't think of a reason why 400VDC optimizer output circuits in the same wireway as 240VAC inverter output circuits and using 600V rated THWN-2 is a safety issue for NEC, even without a barrier. Ditto for residential 600V PV output circuits. 300.3(C) allows this generally, but then 690.31(B) adds the barrier requirement. Doesn't make sense for anything except maybe 1000V or 1500V commercial PV circuits.

I'll have to review if the language has been changed but I think optimizer output circuits are not a problem. Or at least that used to be so. Optimizer output circuits are not PV source or output circuits.

 

[ggunn]

I'll have to review if the language has been changed but I think optimizer output circuits are not a problem. Or at least that used to be so. Optimizer output circuits are not PV source or output circuits.

But they can have higher voltage than 600V.

 

[jaggedben]

But they can have higher voltage than 600V.

Yes but he said 400VDC.

 

[ggunn]

Yes but he said 400VDC.

I know, but optimizer voltages can be much higher than that and 690.31(B) makes no distinction for voltage. 690.31(B) and 300.3(C) are in obvious misalignment but prudence and common sense would imply that compliance with 300.3(C) be acceptable for DC voltages of 600V or less while 690.31(B) would apply to DC voltages greater than 600V.

 

[jaggedben]

Applying common sense to 690.31 seems like an impossible task. (And is ironic coming from you, since you're always making fun of the code for not making common sense). This is especially so after the 2020 re-write, which forces me to take back what I said about 400V optimizer outputs. (And now Class 1 is allowed to mix with raw PV output? How does that make any sense.)

It used to make sense to me that 690.31 was intended to substantially eliminate any fluke possibility of raw PV voltage getting onto AC wiring or being mistaken for it. Since they swept optimizer circuits into it but allowed Class1 to mix, that now makes little to no sense. I now completely agree with Solarken that this section needs another re-write.