Guess what causes this

Here’s a trick question for some folks. Guess what caused the burn marks on this switch. I know, and I’ll post the other picture later. There were several other switches mounted like this with similiar marks.

It stumped me until I came across the last switch. :smiley:

Was there a “dimmer” on the last switch?

Nope… :slight_smile:

Hint: the box itself is plastic.


Jim King

Cigarette butt? or perhaps some other open flame rested on top of the box - candle?

open neutral

I’ll take a guess…

conduit used as ground

interruption of ground continuity by plastic boxes

That’s it.

switch2 (640 x 480).jpg

What’s going on with the paint behind the EMT in pic 1?

Flat paint rolled over a gloss. Crappy paintjob that’s all.

Faked me out. Looked like paint blistering from heat. Darn web photos.