Several years ago myself and one of my employees were replacing a heat pump in the ceiling of a doctor's office. It was about 3am and we were both half dazed from the late hours. Our heat pumps were 480 volt but the replacement they had sent was 208 volt. Of course neither of us bothered to check the tag when we hooked it up. I was on a ladder and turned on the disconnect to check it. The transformer didnt seem to particularly like the extra 272 volts and went off like a 12 gauge. I went backwards off the ladder, crashed on the desk, and hit the floor. Once I figured out i was ok and we hadn't destroyed anything; it was pretty funny. I owned up to my stupidity at the next days shop meeting and wrote "Beware of the Kaboom" on the board. So every time I start up some new equipment or take a project down the road for the first time, I still have the words "Beware of the Kaboom" going through my head.