I was just recently trying to explain this to a European friend who thought I
was hallucinating this system, so I took a picture.
http://dl.dropbox.com/u/230717/temp/208YPanel.jpg
That's a picture of one of the breaker boxes in our office, showing what you described.
There are 3 phases coming into the panel, each a different coil off a Y transformer, as
well as a "neutral". Those are the 4 black wires you see at the bottom. You can
see how the three hot phases are staggered as they go up the breaker rails.
For standard 110V service, you use a single-wide breaker and send one hot phase
+ neutral and you get 110V. The difference between two phases is 208 volts
though, so you use a double wide breaker and can send to device without using a
neutral wire. Just 2 hots and a ground. If that's all you're doing (you don't
need legacy 110V service anywhere) you skip the ground wire going into the
panel entirely.
that one looks dangerous.
In europe:
http://img406.imageshack.us/i/verteilerkasten.jpg/
64A 240V 3-Phase input.
Out to Servers single phase, output to airconditioners with 3 phase (not
at this picture).
Kind regards,
Ingo Flaschberger
