Basics of North American 220-Volt Electricity

• In North America, power enters a residential electrical panel in the form of two hot wires, each stepped down from the transmission voltage of the power lines to approximately 110 volts by a transformer on the lines. One of these wires supplies each 110-volt circuit in the house that powers small appliances, lights and electronic equipment. Circuits powering larger equipment, however, like dryers and stoves, use both wires to produce a voltage of 220 volts. The larger voltage allows the equipment to get the power it needs without overheating the wires.
  
  

Connecting 220-Volt Circuits to the Panel

• Whenever you wire a 110-volt circuit, you connect a single hot wire to a circuit breaker in the electric panel. The breaker makes contact with one of the supply wires coming into the panel via one of the two bus bars. When you wire a 220-volt circuit, on the other hand, you need two hot wires and two breakers. Each breaker is in contact with one of the supply wires via the bus bar to which it is attached, and the voltage across the wires is 220 volts. The breakers are coupled so that they trip together.
  
  

Appliances That Require 220 Volts

• Appliances with an electric heating element commonly use 220-volt power. These include electric furnaces, hot water heaters, dryers, stoves and ovens. Certain high-demand appliances like air conditioners and some fluorescent light fixtures also use 220-volt electricity. These appliances are usually stationary, but some, like shop tools, may be moveable. When a 220-volt appliance has a plug, the plug is configured according to the amperage that the appliance draws and can only be plugged into a receptacle with the same configuration. That receptacle must be wired to a pair of coupled breakers in the panel with the appropriate amperage rating.
  
  

Foreign Appliances

• In countries with 220-volt electricity, that voltage is supplied in a single wire, and the plug configurations are different from North American 220-volt circuits. In many cases, a small appliance from a country with 220-volt power will work satisfactorily in the U.S. if you use a transformer that steps up the voltage in a 110-volt outlet to 220 volts. Not all appliances will work in this way, however, because the frequency of the alternating current in the originating country may be different from that in the U.S. Conversely, you can use most American 110- and 220-volt appliances overseas with the proper adapters.