Dragging this post back to the top because of something that happened recently. Never before have I seen it. I was installing a chandelier on a house that was completed earlier, and the chandelier box was capped off for future use. Whoever trimmed the house stuck a 3 way in the switch box because it had a 14/3 and they thought it was a 3 way but actually it was ran to the chandelier box possibly for a future fan. Anyway not knowing it was a 3-way (Decora), I flip the switch down and climb up to open the box. As I reach into the pancake to fetch the wires I hear a faint crackling, then next thing I know it sounds like a Lincoln Buzz Box and suddenly the red wirenut bursts into flames. I'm trying to grab it with my linesmans and I'm blowing on it but it will not stop burning. Finally I manage to rip it off the conductors and fling it to the floor, where it makes a good burn mark. Whoever trimmed had capped the unstripped red conductor in with the grounding conductor, and the wirenut must have just cut in enough to make for a nice load without enough to trip the breaker (no arc fault). If I had not seen this with my own eyes I wouldn't have believed it. That wirenut would not estinguish for anything. I think of this now everytime I see a flying splice in the attic.
