On 04/30/2018 10:05 AM, Ralph Mowery wrote:
Most places that have equipment that uses lots of power in the US will
have 480 volt 3 phase equipment such as motors. The lights are most
often 277 volts single phase as that is the neutral to one hot leg of
the 480 volt 3 phase circuit.

We leased an old bakery where the freight elevator was 550. After 40
years of home repairs the 550 showed up in the damnedest places. I never
made any assumptions about what I'd find when I opened a panel.