Solar Accessories: Cables and Connectors

In the previous article in this series, we covered the essential safety accessories for an off-grid solar power system. Be sure to read that article, or go back to the first article in this series for a complete overview of how to design an off-grid energy system. In this article, we describe the types of wiring needed to make a complete and safer off-grid solar installation.

Remember, in solar installations the panels and batteries are always on, so make sure that all the breakers are off when making cabling connections. Even so, be careful when connecting batteries together.

Cable Types

Each solar installation will need two kinds of cables: more expensive PV wire for exposed cabling, and less expensive wiring, typically THHN, similar to normal interior household wiring, for protected cabling. In addition, different portions of the system will use different wire sizes, as noted in a later section.

It is also a must that these cable types be stranded. Solid core wires in the gauges necessary are completely unworkable. We prefer a minimum of 19 strand wire.

PV Wire

The soft, spongy-looking black and pink wires shown in the photo below is a special UV-resistant PV wire:

This is the same insulation coating that ships on the cables attached to the panels themselves. This wire is specifically made to be exposed to sun and weather without additional conduit. You should, however, add rubber grommets to the knock-outs to protect the wire from the sharp metal edges. Click on the picture, taken during a demonstration setup, for a much better view.

For sanity, get this wire in both black and red, and then use accordingly.

THHN or Equivalent

In contrast to PV wire, THHN will be less expensive for a given gauge. The photo to the right shows a 500 foot spool of THHN as can be found at various home improvement stores. This spool contains red wire, but it usually also is available in black, green and white. Choose spools in black and red.

Physically, the THHN wire will have a slick and smooth texture, as can be seen in the enlargement of the photo.

Next article: Cable Connectors ...


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