Wiring question. Splicing DC wires.

[max2k]

I know it has been a while... but is the recommendation when making a splice in an outdoor rated j-box to use Unitaps? Any thoughts on Polaris . I will be transitioning from pv wire to thhn on the roof.

soladeck? It would give you sealed roof penetration besides just transition point.

[Atomx12]

I know it has been a while... but is the recommendation when making a splice in an outdoor rated j-box to use Unitaps? Any thoughts on Polaris . I will be transitioning from pv wire to thhn on the roof.

[Sunking]

Not to mention you have a P.E. license and reputation to consider.

Yeah if my stamp is on anything makes me liable in any court. However my comment is based on experience. The Forum owner can be held liable for bad information given on this forum. Not only Liable but can also held accountable for Slander and Malice. Some people seem to think Free Speech means they can say anything they want. That is far from reality.

[J.P.M.]

Smart man, know you now why I duct most DIY code and safety questions. Let someone else tell them the wrong information, so when they burn down their homes they can go to the Forum Administrator and who gave them bad advice for liability law suit. It has happened before and will happen again. Mike Holt has had to buy a house or two. That is why that Forum is only open to licensed professionals.

Not to mention you have a P.E. license and reputation to consider.

[Sunking]

deleted. I should have stayed out of this thread. I've got a bad vibe from this OP.

Smart man, know you now why I duct most DIY code and safety questions. Let someone else tell them the wrong information, so when they burn down their homes they can go to the Forum Administrator and who gave them bad advice for liability law suit. It has happened before and will happen again. Mike Holt has had to buy a house or two. That is why that Forum is only open to licensed professionals.

[Sunking]

That sounds like the definition of "braid", not splice.
Where are you getting that definition from? It's not from NEC.

NEC does not define the word SPLICE. It does use the word "splice" by "listed devices", but Twist-On connectors (proper NEC of a Wire Nut) is not listed for wet, damp, or where exposed to UV locations.

[russ]

I've got a bad vibe from this OP.

A shade tree mechanic type that is trying to go cheap and has no knowledge of electrical systems

[sensij]

deleted. I should have stayed out of this thread. I've got a bad vibe from this OP.

[foo1bar]

The keyword is SPLICE right? The definition of SPLICE is: To Weave or Twist together.

That sounds like the definition of "braid", not splice.
Where are you getting that definition from? It's not from NEC.

The correct term is TRANSITION from one wire type to another which is done with either listed Term Blocks or Compression Taps.

I think the term splice covers that, as it is a more general term - it's any time you are joining the ends of two wires together, even if they are exactly the same size and type (while Transition I believe implies a change from one type to another)

[Sunking]

" 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.

Don't hold your breath thinking that is going to hold up in latter code cycles. CT cable is more than 1 conductor in a common jacket. It is done so the conductors are closely magnetically coupled to minimize CHOKING which is critical for proper OCPD to operate.

[Sunking]

PV listed wire also has sunlight resistance, right?

Yeah that is why I said UV. I understand your point, but code still requires single cables to be in a protective raceway, secured, and protected from physical damage, and to keep the conductors closely coupled magnetically. You cannot lay conductors on asphalt shingles with staples. Eventually wind is going to move cables and the asphalt shingles will wear through the insulation not to mention a nice lunch for TREE RATS, and nesting material for birds. It would have to be some short of SHIELDED Armored Cable meaning more than one conductor in a protective jacket Armour, or CT rated cable in a rack system.

USE-2 is direct underground and does not require a raceway when under ground direct burial. When used above ground it is reclassified as RHW-2 which requires a protective raceway right?

[Sunking]

It looks to me like pretty much all of them think doing a splice (from PVwire to THWN wire) is a good idea (or at least acceptable), while you asserted that "There is no good reason to have any splices. Would indicate a poor design and/or workmanship."

The keyword is SPLICE right? The definition of SPLICE is: To Weave or Twist together. That is what a wire nut does. The correct term is TRANSITION from one wire type to another which is done with either listed Term Blocks or Compression Taps. If an inspector opened up a J-box and found wire nuts used in wet or damp locations would fail the Inspection. IMO that constitutes poor design and/or workmanship likely to result in a failure and possible fire hazard.

[bcroe]

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. "

Glad to hear that; I added 6' of cable tray to an unsupported run. Very little heat
there, but getting those 2 dozen wires into conduit would have meant dismantling
it all. Perhaps it doesn't meet the "secured at least every 4.5 feet" requirement
unless snapping on the lid counts. Could add a tie down in the center; gravity
is doing well right now. Bruce Roe

[sensij]

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.

PV listed wire also has sunlight resistance, right? So it can be run without conduit (like USE-2), but THHN-2 can't. That's why it can make sense to do the rooftop with open PV wire, then transition to conduit with THWN-2 (or whatever is appropriate) and save some money on the rest of the home run.

[foo1bar]

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

Post #1 in this thread abolev1984 said
"And using wire nuts for splicing..Big deal?"

And he/she has re-iterated the plan to use wirenuts since then too.

Or maybe you misread me - I said they (Mike Holt forum members) are NOT using wirenuts (and I wouldn't either).


It looks to me like pretty much all of them think doing a splice (from PVwire to THWN wire) is a good idea (or at least acceptable), while you asserted that "There is no good reason to have any splices. Would indicate a poor design and/or workmanship."