A friend and Electrical Contractor who shall remain nameless was drilling through the top of a can to tie in a new genny transfer switch for a turkey barn. No power-off was allowed and Y2K was looming, so he chose to do the work hot. When the hole saw broke through, it went straight into a 120V leg of a 120/240V 400Amp service and burst into flaming arcs of molten saw teeth. He was miraculously uninjured, but was shaken up for days. He did the rest of the barns with the services open.
