I believe ITO's covered it well.

Something that a whole lot of people need to keep in mind is that there is no 220V.
I see otherwise accomplished electricians talking 110 and 220 in their advertisements and everyday speech, and I just don't understand why.
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From 220.5(A) Voltages.
Unless other voltages are specified, for purposes of calculating branch-circuit and feeder loads, nominal
system voltages of 120, 120/240, 208Y/120, 240, 347, 480Y/277, 480, 600Y/347, and 600 volts shall be used.



[This message has been edited by electure (edited 03-04-2007).]