Putting new light fixtures into an old house. Wires are stranded copper with a little paint on some of the stranded copper part.
Normally I'd cut it off and expose a little more wire, out of an abundance of caution. The thing is, this is an extremely short wire coming directly out of a massive bundle of wires… it would be next to impossible to strip off a little more insulation and twist my wire nut on.
Is a little paint a hazard for two stranded copper wires twisted together in a wire nut? There is plenty of copper-to-copper contact within the wire nut… but some of it will have paint in the way. Can this cause sparks or heat? (Will be behind an AFCI breaker.) Or will the electricity just flow through the low-resistance areas where the copper is touching directly?
Best Answer
Paint can act as an insulator so is it a hazard not normally. Wire nuts cut into the wire slightly so the nut itself makes contact if nothing else.
Best practice would be to use a bit of sandpaper or scotch brite to clean the paint off and provide a better connection.
In motors the red varnish is really thin. A 3m rep showed how well scotchlocks (there wire nut brand) did in creating good contact with varnished wires (sales pitch) but in my experience all the brands do about the same as long as they have the metal.
So scrape the paint for best results, tighten the nut until the wires twist below the nut according to the brand you like instructions.