Wiring question. Splicing DC wires.

[Sunking]

What is the issue with PV wire in conduit;

Nothing from a code perspective, it is a budget issue. The only technical difference between PV Listed Wire and THHN-2 is Voltage rating and UV, PV listed wire is rated for 1000 volts vs 600 for THHN-2. If you are in Europe that has an advantage but not here in the USA where voltage is limited to 600 volts. So it makes little sense for a contractor to pay twice as much for wire that has no usable advantage.

[Amy@altE]

Thanks Sensji, I thought it had something to do with the insulation and heat build up. I might have been thinking about that. Thanks for the clarification.

[Living Large]

Philosophically, I'd suggest it makes no sense to use wire nuts to connect the conductors of the DC power source to a house. If some resistance builds up, that puppy is going to fry.

Personally, it seems like this is one place to do the job right and not try save a few bucks.

[sensij]

What is the issue with PV wire in conduit; metal or plastic? I know I have a couple dozen
wires in a cable management tray to keep things organized, leading to the combiner box
by the ground mount PV. Bruce Roe

No problem with conduit. Cable tray was questionable, but NEC 2014 made this clearer. Snipped from this writeup:

Cable tray is a popular wire-management device for all sizes of systems, but the requirements in other sections of the Code about its use with smaller conductors, such as those used for PV source circuits, were confusing. Section 690.31(C)(2) now explicitly allows use of cable tray for PV-source and output circuits if they are listed PV wire, even when it’s not marked for use with cable tray. The enhanced durability of PV wire led to this allowance, along with the realization that, especially on commercial rooftop systems where thermal movement and expansion and contraction can wreak havoc, conduit may not always be the best installation method for conductors. The conductors in cable tray must be supported at least every 12 inches, and secured at least every 4.5 feet.

[bcroe]

It's not so much a splice as transitioning from PV Wire from the panels to THHN in the conduit to inside. Which requires a pass-thru box, not wire nuts. I don't have my code book on me, but I thought PV wire was not supposed to go in conduit, thus the transition. I may be wrong, it could just be a cost thing, THHN is much less $ than PV Wire.

What is the issue with PV wire in conduit; metal or plastic? I know I have a couple dozen
wires in a cable management tray to keep things organized, leading to the combiner box
by the ground mount PV. Bruce Roe

[Sunking]

There's apparently at least 3 people who disagree with that:
http://forums.mikeholt.com/showthread.php?t=168428

But they're not using wirenuts either, which I would not do.

Tell me exactly where they say to use Wire Nuts for Transitions.

FWIW I am a Moderator on Mike Holt for the last 13 years, so I might know a thing or two about code.

[sensij]

It's not so much a splice as transitioning from PV Wire from the panels to THHN in the conduit to inside. Which requires a pass-thru box, not wire nuts. I don't have my code book on me, but I thought PV wire was not supposed to go in conduit, thus the transition. I may be wrong, it could just be a cost thing, THHN is much less $ than PV Wire. Either way, don't use wire nuts in a moist location exposed to heat/cold. They will fail.

This. Check out Soladeck for an example.

[SunEagle]

Or you can do what a lot of electricians do in the field. They use split bolt connectors and a lot of 3M black electrical tap.

[russ]

There's apparently at least 3 people who disagree with that:
http://forums.mikeholt.com/showthread.php?t=168428

But they're not using wirenuts either, which I would not do.

Lots of people may disagree - no big deal as they are allowed to be wrong.

[Amy@altE]

Wire nuts are not permitted in damp or moist locations for power and lighting. End of story. There is no good reason to have any splices. Would indicate a poor design and/or workmanship.

It's not so much a splice as transitioning from PV Wire from the panels to THHN in the conduit to inside. Which requires a pass-thru box, not wire nuts. I don't have my code book on me, but I thought PV wire was not supposed to go in conduit, thus the transition. I may be wrong, it could just be a cost thing, THHN is much less $ than PV Wire. Either way, don't use wire nuts in a moist location exposed to heat/cold. They will fail.

[foo1bar]

There is no good reason to have any splices. Would indicate a poor design and/or workmanship.

There's apparently at least 3 people who disagree with that:
http://forums.mikeholt.com/showthread.php?t=168428

But they're not using wirenuts either, which I would not do.

[Sunking]

Wire nuts are not permitted in damp or moist locations for power and lighting. End of story. There is no good reason to have any splices. Would indicate a poor design and/or workmanship.

[Mike90250]

Wire nuts are NOT for exposed locations. Maybe for a low power lawn sprinkler system, but not utility power where they see weather hot cold cycles, moisture condensing on them....... Wire nuts OK indoors on lower amps wiring.

[abelov1984]

I guess I did, but with your help..

However wanted to hear electricians, saying something about prevent dc arching, and about long term of wire nuts splicing (that are on the market right now) like 15-20 years. Inspection here won't go on the roof, but I'm wondering about quality of installation.
Thx

[Living Large]

unitaps are too expensive, compare to wire nuts.

It sounds like you have answered your own question. Use the wire nuts if that is what you want - you will have to determine for yourself if it is a big deal.