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Ralph Mowery

In article ,
says...
Commercial lighting should make you happy though since it is usually
277 volts.

Why 277?!

One phase of a 480wye.

Why do they use 480?

Same reason you are pimping for 220. It allows smaller conductors for
a given amount of delivered power. 480 is common for services to large
installations like office buildings and gets distributed to each floor
as 480 where a transformer will take that down to 120/240 or 120/208.
The house lighting will usually be 277 using one 480v phase to
neutral.

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.

Really big users will have even higher voltages. The plant I worked for
had a power room where the power from the electric company was converted
from whatever they sent us to 13,200 volts. This was sent to other
parts of the plant where it was mostly conveted to 480 V 3 P. There was
some equipment that used around 4,000 volts. I did not usually work
with that and don't recall the exect voltage, want to say 4100 volts.

Then we got is some junk from Europe that used 380 V 3 phase. They even
reversed the safety color code on the main disconnects. To the US it
was green for power on, and red for power off. Their junk was green --
power off--safe to open the door to the electrical box. Red was power
on-- not safe to open the door.

Once the color code for danger (off/on) is changed there might as well
not be one. Probably safer if not used.