Wiring Methods for Solar PV Panels

[Nick Ladomirak]

We're reviewing a solar PV installation on a roof. The installation is in conduit only where accessible to the public, such as on the side of the building. On the roof it is wired with USE-2 and basically ty-wrapped. Is there an issue with this installation in regards to the Code? I can't find a reference to wiring on the roof needing to be in conduit because it is out of reach, but generally we see them in conduit.

 

[iwire]

Somewhere in the PV article that says we can run single conductor USE and I think other types under the same rules as UF cable at the array.

 

[jaggedben]

Raceways are only required if the conductors are readily accessible. See 690.31(A) and 690.31(C)(1).

Another section that could be applied is Article 338, for USE-2, which points to a section of Article 334 regarding support.

If it's really sloppy work, e.g wire just laying on the roof, then they may be running afoul of temperature limitations with 310.15(B)(3)(c). And there's always 110.12 as well.

But if the conductors are properly supported, say all tie wrapped to rails or in laid a strut channel or something, I don't believe that's a code violation.

 

[Carultch]

We're reviewing a solar PV installation on a roof. The installation is in conduit only where accessible to the public, such as on the side of the building. On the roof it is wired with USE-2 and basically ty-wrapped. Is there an issue with this installation in regards to the Code? I can't find a reference to wiring on the roof needing to be in conduit because it is out of reach, but generally we see them in conduit.

That's gonna fall apart in a couple of years. Plastic able ties don't last very long in the outdoor exposed environment, no matter how many certifications are on the datasheet. No code rule against it though.

 

[SolarPro]

This article on PV Array Wire Management includes feedback from inspectors and Code experts. It's a tricky topic because what works in Texas won't necessarily work in Pennsylvania where snow is an issue.

Generally speaking, I think UV-rated cable ties can be part of an acceptable wire management solution. However, plastic cable ties are generally best used in concert with other products and methods that provide more permanent support. We would typically use cable clips to route the PV Wire along or across module frames, then use UV-rated cable ties as a secondary or tertiary wire management method. If the cable tie connection needs to last the life of the system, you need to use materials like stainless steel that will last the life of the system.

At this point most racking and mounting providers have products that are a better primary wire management solution than plastic cable ties.