Solid Core Wiring

[Sjaxkingpin]

Trying to find a good answer is frustrating this newb as there seems no shortage of contradictory info even on this forum.

If it isn't a code question, if it is large enough to handle the ampacity, and if it's a fixed setup so no work hardening, is there any issue with using Romex (solid core wiring) for DC interconnections with solar?

 

[Maast]

No issue at all, amp is amps and copper cross-section is copper cross-section.

The only drawback is the stiffness and difficulty making connections as its extremely difficult to make good crimp connections with solid wire unless you use a hydraulic crimper or you solder them. Which is why home AC wiring is done almost exclusively by twisting wire together or by screw-down terminals.

You do have to be aware of the wire insulation value and temperature rating but as long as you meet those requirements you're good. Wire capacity is derived from the temperature rise of wire by the number of amps going through it _vs_ the temperature rating of the insulation material and how well it can eliminate heat. Which is also why wires bundled together have to be derated because they can't eliminate heat as well as a wire in air by itself.

'Solar' wire has a silicon insulation that has a higher temperature rating so it has a slightly higher ampacity rating for the same diameter of copper in it.

I'll be using romex to run 250v DC about 90 feet from the combiner box to the charge controllers.