PV wire and dual-rated solar cable

PV wire is its own listing

PV wire is a single-conductor cable made to UL 4703 rather than to the building wire articles, and it is rated for direct sunlight, ozone and the temperature swings of a rooftop. Insulation is a thick XLPE wall, usually 1 kV or 2 kV, and the jacket print will name the standard as well as the temperature and wet ratings.

It is not the same product as RHW-2 even when both are XLPE. PV wire is built to be exposed on a rack and terminated in a field-crimped connector, and its insulation thickness reflects that. Treating the two as interchangeable is the most common mistake in a solar electrical package, and it shows in a lot as cable that cannot legally be used where the buyer intended.

What the dual rating buys

USE-2 is underground service entrance cable, rated for direct burial and for wet locations. RHW-2 is a building wire rated for wet and dry, with a flame-resistant jacket. A cable printed with both is dual rated, and it can be run underground to a combiner and then continue exposed on the array without a transition.

That dual rating is why so much of this cable is bought in one size and used everywhere on a project. It is also why leftovers are common: an installer orders for the longest run and keeps the balance, and the balance is often a part reel of the same construction that started the job.

Solar in Ohio

Utility-scale solar has moved onto the flat farmland of northwest Ohio, where Hardin and Wyandot counties hold large arrays on former crop ground, and onto the gentler ground in the southwest. Those builds use enormous quantities of single-conductor cable, mostly direct buried, and a project that is re-phased or resized leaves reels behind at a laydown yard.

Rooftop work is smaller and more scattered: warehouses, schools, municipal buildings and commercial roofs across the Columbus and Cleveland suburbs. The leftovers there are short string offcuts and part reels, usually stored in a connex box with the mounting hardware, and the condition question is almost always about sun and water rather than about handling.

• Print showing the PV standard and the voltage rating
• Sunlight and wet ratings legible, not faded out
• Reel wrapped and stored out of direct sun
• Connectors cut off clean, not crushed

What degrades a solar cable lot

Ultraviolet exposure is the first thing. Cable left on a rack for two summers will have a chalky jacket and a print that has gone from black to gray, and while the insulation underneath may still be sound, the marking is what a future inspector needs. Faded print narrows the use.

Water wicking at a cut end is the second. The strands in a fine-stranded PV conductor will pull moisture a surprising distance under the insulation, and the end shows it as dark copper rather than bright. A lot with dry, bright ends and intact print reviews cleanly even if the reel has been sitting for years.