I went to troubleshoot a tripped breaker, and after taking all the load off of the circuit and putting on one lite at a time, I still could not narrow it down to any one thing. I did find that someone had used a ground for a neutral for the return of about 4amps for some lites(It was done so the homeowner would have a 3way) After about 3 hrs of tracing each wire, this is what was found in a boxed out a/c return.
Yes, or a staple. There was a staple next to it. I might have smelled it burning, but the heat was set at about 80, and the return was constantly pulling the air in. They are really lucky.
It was in the dining room wall, they had a pipe on the secound floor burst, and the water made its way to the hole in the wire. As the connection between the hot and the ground/neutral was made, the wire heated and the breaker tripped.I think the water could have bubbled, and thats why it took so long to trip.