We had an "electrician" in helping us with the wiring involved with installing three screw compressors. I started to have suspicions when he called me over a couple of times to ask me what color a particular wire was. He was color-blind and they all looked gray to him. Anyhow, He had finished wiring up the starter of a 250 HP motor and apparently didn't like the way it was pulling in the contactors.

I was doing something across the room and happened to look over again just in time to see him pushing something in the panel with a long 2x4. He broke and defeated the mechanical interlock between two contactors and shorted out all three phases.

Fireball. Luckily he was back far enough to avoid anything serious.