Originally Posted by
Macspreader
Now taking these yellow boxes and callng them 110V is actually a misnomer - they carry 55V in two conductors out of phase with each other, and keep the earth at 0V, so unless you're really unlucky you'll get a 55V shock.
I've done a fair amount of wiring here in the US.
220V service is pretty much as you described -- 120V in two conductors out of phase. This is used on a few high-power appliances (air conditioner, dryer, water heater, range, etc.).
However, 120V is provided using one of those conductors (called "hot") and "neutral", which is tied to earth at the service entrance. A third conductor also tied to earth is provided at outlets. Ideally, the neutral line and earth should both be at 0 volts, but for various reasons they might not be.
So the hot wire will always have 120VAC between it and the neutral line and earth.