When Conduit is an Absolute MUST (Code Requirements). The National Electrical Code (NEC) in the U.S. and similar regulations elsewhere are very clear on this. You absolutely must run solar cables inside a conduit when they are installed in readily accessible locations or pass through the interior of a building.
This includes situations where your PV cables:
- Run inside your attic, garage, or living space. Once they leave the array and enter the building envelope, they need to be in conduit. No exceptions.
- Are installed in locations where they could be subject to physical damage. This is a bit of a judgment call, but think about areas near walkways, driveways, or places where you might be using a weed whacker or lawnmower. If there’s a reasonable chance something could hit, cut, or crush the cable, it needs protection.
What happens in a solar power system that doesn’t have a solar cable conduit? I’ve seen unprotected, high-quality PV wire destroyed by squirrels who decided it was the perfect teething toy. I’ve seen cables degrade prematurely after years of being buried in rocky soil or getting whipped by branches in a storm. These are costly, frustrating problems that a few lengths of conduit would have completely prevented. Even if your cable meets the standards for direct burial and UV protection, I still recommend using ductwork for outdoor wiring: it provides an indestructible barrier, resist rodents, sharp rocks, accidental shoveling, and unforeseeable impacts. The neatly laid-out pipes also look cleaner, more professional and more organized.
