Arc Gremlin Beside my Front Door
Sunday, I was prepared to replace the switch that controlled my front outdoor light. It had stuck in the “on” position and having a couple fail in the same way, I pulled the three-gang switch plate off and found a mess. Rather a mess that made my heart miss a few beats. I forgot to take pictures of the burned wiring inside the box, but saved the switch to photograph.
Looks like a catastrophic failure to me; at first I had blamed it on a poor connection until I saw the flash marks.
The fracture was not caused by removing the switch, it was already there. You can also see remnants of melted insulation on the back of the switch.
I an sure it ejected some flame here when it happened. I was unable to get a good inside picture of the backside of the handle. I’ll update later if I do get one. The screw looks corroded, but I found no sign of water having been anywhere near the switch.
From what I can tell, the flash incident went unnoticed. We rarely switched the automatic outdoor light off. One night I noticed that the light was staying on (it is a motion light), so I went to turn it off and found the switch stuck “on”. I did not notice the melted plastic for several days until after I went to replace the switch. It seems that the line from the breaker entered the quick connect hole (I hate those things!) and the rest daisy chained off the screw terminal to the other two switches in the box, and the rest of the circuit and overheated, melting the insulation. The melted insulation pattern was not consistent with a single flash incident. I have seen insulation blown off of wires and stuck to other objects inside the box, where the bulk of the missing insulation here was obviously split away from the conductor.
The frightening thing is that we have a coat rack right next to the switch box that could have easily caught fire if a coat was covering the switch. Any guesses as to my next project? Hint: The coats are moving to a different location!
