Now everyone can possess the whole of human knowledge on the subject
(Actually, I stole this off another site)[)]
I think its time for me to explain about 220 current and why it is so different from 110 volt service. First of all, it's twice as big.
Secondly, it'll shock you more. Outside of that, 220 is really two 110 volt lines coming to your house from different parts of the globe.
The up and down 110 comes from the northern hemisphere, and the down and up version comes from below the equator.
Without trying to get technical, it all boils down to the direction water flows when it goes down the drain. In the top of the earth, it goes clockwise, while on the bottom of the earth it goes counter clockwise. Since most electricity is made from hydro dams, the clockwise flow gives you an up and down sine wave, while the counterclockwise version gives you a down and up sine wave. Between the two, you have 220 volts, while either individual side only gives you 110 volts.
This is partiularly important to know when buying power tools- which side of the globe did they come from? If you get an Australian saw, for instance, it will turn backwards if connected to a US generated 110 volt source. Sure, you can buy backwards blades for it, but that is an unnecessary burden. Other appliances, like toasters cannot be converted from Australian electricity to American electricity, without horrible results. I knew one person who bought an Australian toaster by mistake and it froze the slices of bread she put in it.
If you wire your shop with 220 and accidentally get two US-generated 110 volt lines run in by accident, you can get 220 by using a trick I learned from an old electrician. Just put each source into its own fuse box and then turn one of the boxes upside down. That'll invert one of the two up and down sine waves to down and up, giving you 220. DO NOT just turn the box sideways, since that'll give you 165 volts and you'll be limited to just using Candian tools with it.