My house came with a 100A box with six breakers, all unlabeled. One of them did nothing at all when I flipped it, another produced a loud humming for three or four seconds before tripping off. I still don’t know what the humming was but when I rebuilt one of the walls I found a big scorch mark on the stud next to one of the outlet boxes so I suspect that was involved. The one that did nothing it turns out was connected to an MC cable that had simply been sawed off clean – not even some electrical tape wrapped around the cut end – and jammed down into the framing completely live. At least I was able to repurpose that one into a circuit with receptacles and lights in the attic.
My house came with a 100A box with six breakers, all unlabeled. One of them did nothing at all when I flipped it, another produced a loud humming for three or four seconds before tripping off. I still don’t know what the humming was but when I rebuilt one of the walls I found a big scorch mark on the stud next to one of the outlet boxes so I suspect that was involved. The one that did nothing it turns out was connected to an MC cable that had simply been sawed off clean – not even some electrical tape wrapped around the cut end – and jammed down into the framing completely live. At least I was able to repurpose that one into a circuit with receptacles and lights in the attic.