Helping the boss install a Delta-480v main fire station. We replaced a 1980s unit with a brand-new, half-sized, computerized unit. Had 2 feeds coming in overhead, one was back-up/emergency from a generator and one was main feed. He pulled the old feeds out and placed them in the same way. On the new unit, the emergency was on the other side. Checked continuity on all phases...except the last one. Both of us completely forgot for some reason. Flipped the disco, kaboom. Phase C was grounded. Grenaded the solid copper on the inside and turned the crimp sleeve nice and black. Almost tore a hole out of the side.
Running Romex in a remodel house. Walking through the attic only not to see a telephone cable running along the joist, trip, kaboom. Size 12 through the ceiling.
