I was troubleshooting a burning smell when I pulled back a piece of paper-backed insulation. The insulation had a black mark about 18" long where the romex had burned it, and the romex had brown burn marking on the romex for about 18". (These are 120 volt fluorescent fixtures with magnetic ballasts). The ballasts were very hot to the touch but the whole circuit was drawing 4 amps. My thoughts are that the heat from the ballasts caused the burning. Has anyone else come across this before?

The answer depends on where the romex was in relation to the ballasts..was it touching them directly or laying on the fixture? And did the burn marks line up with the ballast location? If not, then there is some other issue at work here....and note that a standard magnetic ballast can run very hot to touch normally.

And did you get and pictures?

Well how hot were they? Sounds like too hot.

The romex was in the attic. There was sheetrock between the wire and the fixture with insulation on top of the wire (paper-backed). With the wire only being burnt about 18" past both fixtures, I think the copper transfered the heat from the ballasts that far, and the insulation kept the heat from dissipating. Sorry no pictures. I need to take my camera with me, that would be a great idea.