Another PV wire question

[Jeff S]

We have some upcoming systems that will be 1000V ungrounded systems using Power-One Inverters. I'm clear on the fact that we need 1 or 2KV rated PV wire where it's exposed on the roof. I'm also clear on the fact tht USE-2 isn't permitted inside a building unless it's dual rated with a rating that is smoke resistant. So my question is, Can RHW-2 (2KV) be used for 1000V in conduit once it's transitioned from the PV wire in a rooftop J-box?
Also, I'm aware that fine stranded wire can only be used in terminals rated for fine stranding or else you must use a crimp sleeve. What I can't find is anything clearly defining fine stranding. Is that the Class B numbers in Chap 9 Table 10? More specifically if I'm using #10 (19 strand) PV or RHW-2 wire, can I directly connect it to the lugs on load center circuit breakers?
Does anyone have a suggestion about where to find 1000V UL rated terminals for the rooftop wire transition box? The Allen Bradley 1492-J10 terminals that we normally use carry a 600V UL rating and a 1000V IEC rating. Will inspectors accept the IEC rating?
Thanks,
Jeff Schmidt

 

[jaggedben]

Okay, I haven't done any systems over 600V, but here goes...

So my question is, Can RHW-2 (2KV) be used for 1000V in conduit once it's transitioned from the PV wire in a rooftop J-box?

I don't know why not. Applicable ampacity tables in 310 go up to 2000V.

What I can't find is anything clearly defining fine stranding. Is that the Class B numbers in Chap 9 Table 10?

I'm not sure what the definition is, but I don't think there's any fine-stranded conductors in that table, and they're definitely not the class B numbers.

More specifically if I'm using #10 (19 strand) PV or RHW-2 wire, can I directly connect it to the lugs on load center circuit breakers?

That's not fine stranded wire, so whatever you terminate in does not need to be listed for that. But...Load center? Do you mean combiner? If you are doing a system over 600V I think you need to make sure all the DC equipment is listed for 1000V, and if the literature does not specify the allowed wire sizes, then ask the manufacturer.

Will inspectors accept the IEC rating?

I think you'd better ask your AHJ.

 

[Jeff S]

Thanks for your response.

Thanks for your response.

"That's not fine stranded wire, so whatever you terminate in does not need to be listed for that. But...Load center? Do you mean combiner? If you are doing a system over 600V I think you need to make sure all the DC equipment is listed for 1000V, and if the literature does not specify the allowed wire sizes, then ask the manufacturer. "


Sorry, I meant to say where they terminate in the inverter. I've done so many AC module systems lately that I had the AC combiner panel (load center) stuck in my head.

I find it interesting that in several training courses and in articles they've mentioned the fine stranding issue but no one seems to have specifics. I agree that 19 strand #10 PV wire shouldn't need anything different than how you terminate 19 strand #10 THWN-2. I don't really know where they're coming from about the fine stranding.


Thanks for your input,
J.S.

 

[jaggedben]

Somebody on this forum ought to know the answer. Maybe start it as a new thread titled "definition of fine stranded".

 

[marti smith]

110.14 Electrical Connections. See related ROP UL

Changed From 2008

?110.14: Revised by adding a second paragraph to require that terminals and connectors used with conductors that have other than standard stranding shall be identified for the specific conductor class(s). A new Table 10 has been added to Chapter 9 to provide information on conductor stranding.

Because of different characteristics of dissimilar metals, devices such as pressure terminal or pressure splicing connectors and soldering lugs shall be identified for the material of the conductor and shall be properly installed and used. Conductors of dissimilar metals shall not be intermixed in a terminal or splicing connector where physical contact occurs between dissimilar conductors (such as copper and aluminum, copper and copper-clad aluminum, or aluminum and copper-clad aluminum), unless the device is identified for the purpose and conditions of use. Materials such as solder, fluxes, inhibitors, and compounds, where employed, shall be suitable for the use and shall be of a type that will not adversely affect the conductors, installation, or equipment.

Connectors and terminals for conductors more finely stranded than Class B and Class C stranding as shown in Chapter 9, Table 10, shall be identified for the specific conductor class or classes.

No definition found as of yet...

 

[Jeff S]

Thanks, I think the key here is that the wire we plan on using is not more finely stranded than Class B so we should be fine.
I appreciate the responses on here.
J.S>

 

[Zee]

Jeff S.:
19 strand , #10 wire is Class C. Still seems to be OK, and NOT fine stranded.

Marti Smith:
I am guessing - as i think you are - that strands greater than classes B AND C is certainly "fine stranded".
I agree, "fine-stranded" is not under Article 100 - DEFINITIONS.

I think that NEC 110 section you quoted is the "definition".

 

[jaggedben]

I think that NEC 110 section you quoted is the "definition".

I agree. Good enough for me. Thanks.

 

[Jeff S]

Thanks to all for your input.
J.S.

 

[SolarDude]

I was told the PV wire can not be in conduit unless it is readily accessible. per 690.31(B)

 

[jaggedben]

I was told the PV wire can not be in conduit unless it is readily accessible. per 690.31(B)

690.31(B) permits PV wire in exposed locations. It doesn't prohibit it inside conduit. However the informational note reminds us that a bigger conduit may be needed.

Since PV wire is more expensive and often requires bigger conduit, it usually doesn't make sense money-wise to put it in conduit. But it is allowed.

 

[Jeff S]

690.31(B) is allowing it to be run under the array as single strand just like USE-2 and the exception means that if you can walk on it, you must run it through a piece of conduit. I had also heard that you can't use USE-2 cable inside a building based on 338.12(B)(1) because it's not flame retardant rated. That said, I spoke with the manufacturer of a PV cable and he pointed out that their 2KV PV cable is also rated for USE-2, RHH or RHW-2 and is flame rated VW-1. According to them, since RHW-2 is rated for running in conduit inside a building, we should be fine using it that way.
Any other thoughts on this subject would be appreciated.
As to the previous comment about asking our AHJ (this is the answer given to many questions), we deal with many different AHJ's and they generally leave it up to us to provide proof that what we're doing is O.K. The most common thing they ask for is the UL stamp. The only terminals I've found rated 1000V are rated by IEC for 1000V but have a 600V UL listing. Apparently it's quite difficult to find terminals, wire etc. that carry the 1000V rating. The above PV wire manufacturer pointed out that some things that carry a 600V rating in the U.S. carry a 1000V rating for the same item in Canada.
I'm not looking forward to the inspection of our first 1000V solar installation.
J.S.

 

[jaggedben]

As to the previous comment about asking our AHJ (this is the answer given to many questions), we deal with many different AHJ's and they generally leave it up to us to provide proof that what we're doing is O.K. The most common thing they ask for is the UL stamp. The only terminals I've found rated 1000V are rated by IEC for 1000V but have a 600V UL listing. Apparently it's quite difficult to find terminals, wire etc. that carry the 1000V rating. The above PV wire manufacturer pointed out that some things that carry a 600V rating in the U.S. carry a 1000V rating for the same item in Canada.
J.S.

Yeah, I get what you're saying. From what I've heard, some AHJs will be sticklers for only accepting the UL rating, where as others will accept other labs or standards if you can satisfy them that they are widely recognized. I'm not sure there's an easier way than just asking. If you don't want to ask the AHJ then ask others who have worked with that AHJ. Try asking in the Solar Pro forum, see what people's experience has been with certain products.

As for IEC, my understanding is that it makes standards but doesn't test products. So I would guess that the terminals you mentioned are tested by UL to 600V for the UL standard and 1000V for the IEC standard. You could try to confirm that with UL or the manufacturer. If the AHJ isn't one of those sticklers they'll probably accept the IEC standard.

 

[Zee]

Jeff S.
"I had also heard that you can't use USE-2 cable inside a building based on 338.12(B)(1) because it's not flame retardant rated."

Well..... yes and no.

Back in the day USE-2 was not flame retardant.
Today almost all of it is that i have seen.
So, yes, it does have to be flame retardant, but if it is, then you can run it in conduit inside a building.
(I forget which marking indicates it's flame retardant.......)