Your Home's Electrical System

• Electricity coming into a house is carried on three lines--two carrying 120 volts and a neutral line. All of these wires connect to the home's service panel, commonly known as a breaker box. The live wires each connect to a separate bus bar, which in turn are connected to the circuit breakers. The neutral line connects to its own bus bar.
  Normal household circuits for fixtures and outlets are connected through the breaker to a single hot bus bar and the neutral bus. For 240-volt circuits, a line from each hot bus bar and the neutral bus are connected to special 240-volt receptacles.
  In addition to the difference in voltage, 240-volt circuits have different amperage, as well. Standard home circuits are 120 volts and either 15 or 20 amps. A 240-volt circuit has an amperage ranging from 30 to 60.
  
  

Wiring a Heavy-Duty Circuit

• Only one appliance can run on each 240-volt circuit. Therefore each heavy-duty circuit must be individually wired from the service panel to the receptacle. The first step is to make sure your service panel can accept a 240-volt circuit. If there are at least two adjacent unused circuit breaker spaces in the panel, then you can add a heavy duty circuit--after you ensure that the main switch on the panel is off. If there are no slots available to add a 240-volt breaker (which takes up twice the space as a 120-volt one), then an electrician will have to install a larger panel.
  It is important that you install a breaker with the correct amperage for the appliance you intend to connect to the circuit. The amperage also determines the gauge of wire you will need to install. The American Wire Gauge system uses a number code to describe the maximum voltage and amperage a given wire can accommodate.
  Once the breaker is installed, you will have to run the wires from the service panel depending on the location of the receptacle and your personal preference. If you are running the wire from one end of an unfinished basement to the other, then simply run the wires along the ceiling joist and use electrical conduit to mount the receptacle on the wall. In other situations you may have to "fish" the wires up from the service panel and behind walls to a wall- or floor-mounted receptacle.
  After running the wires, connect them to the receptacle according to the manufacturer's directions. Finally, after double-checking that the power to the service panel is still off, attach the hot wires to the circuit breaker and the neutral wire to the neutral bus bar.