Yup, it happened again...
Yesterday, doing an institutional re-model, I killed all three circuits in the box. I then opened the neutral- and saw a spark.
The neutral measured 50 volts to ground. It was, on the "load" side, definitely hot. We later found a number of fried surge protectors. The explanation: somehow another two circuits had been tied into that neutral. When I opened the connection, the voltage on the circuits became 208.
Properly done, and maintained, sharing a neutral can be a great technique. Give time, and Mr. Murphy, a chance however, and you've got troubles.
As I've said before, we have got to start identifying our neutrals. We also have to be wary of partly trained personnel trying to take this nifty "shortcut."
Finally, contrary to popular belief, the "white" wire is quite often "hot," and you might never find the way to shut it off completely.
