Nearly every residential service panel in the US has two 120-volt wires and one neutral wire running to it from the utility company. Each wire powers one “bus†(copper vertical leg) inside the main service panel. That’s why you usually see two columns of breakers (or fuses) when you open your service panel door. The common 120-volt circuits that power everything from your lava lamp to your vacuum cleaner are powered from one of those two buses. The standard 15- or 20-amp circuit breakers work by clipping onto one of the buses. Then the circuit’s hot (red or black) feed wire is clamped to the circuit breaker, while the neutral (white) wire and bare copper ground wire are clamped to the common neutral bar.
The way you get a 240-volt circuit is simple. A “double-pole†circuit breaker is clipped into both 120 buses at the same time, so the voltage to the circuit is doubled. That’s why 240-volt circuits need two hot wires and a neutral to carry the electricity to the appliance, plus a ground wire.
With a 240V circuit the 2 120V legs are cycling opposite each other at 60htz in the US. The wiring to a receptacle and the receptacle itself requires special wiring considerations to be in code compliance.
WARNING: PLEASE HIRE AN ELECTRICIAN TO DO THIS WORK IF YOU HAVE NEVER DONE THIS BEFORE AND ARE NOT TRAINED IN THIS AREA - this can be very dangerous and could easily kill you if you are not exactly sure of what you are doing!!!!!!!!!
