The Proper Wiring & Receptacle Termination for a Home

Receptacle Circuits

• Lighting circuits with receptacles are found in living rooms, bedrooms and other rooms where the primary need for electricity is for lighting. Homeowners can plug lamps, computers and other small appliances into lighting circuit receptacles. These circuits provide 120 volts at up to 15 amperes. Small appliance circuits are found in kitchens and sometimes bathrooms. They supply 120 volts at 20 amperes. Large appliance receptacles provide 240 volts and allow current in the range of 20 to 50 amperes.
  The wire sizes used in the various circuits depend on the number of amperes allowed. A 20-ampere circuit, for example, requires a minimum of 12-gauge wire.

120 Volts

• Receptacles that supply 120 volts have two wires that carry current, and another conductor for the ground. The ground conductor might be metallic conduit in some parts of the country, a bare copper wire if sheathed cable was used, or a green wire in other cases.
  The colored hot wire supplies current to the receptacle and connects to the narrow slot on the receptacle. A white neutral wire connects to the wide slot on the receptacle. A green terminal screw connects to the ground conductor.

240 Volts

• Some appliances require 240 volts, while others require a combination of 240 volts and 120 volts. New installations require a grounded receptacle. A 240-volt receptacle has two hot wires without a neutral wire. Each hot wire carries 120 volts for a total of 240 volts. The two receptacle slots connect to the two hot wires. Receptacles that supply both 120 volts and 240 volts have a third, current-carrying neutral wire and two hot wires. One of the hot wires and the neutral wire supply 120 volts while both hot wires together supply 240 volts.

Terminations

• Three main types of terminations are found on receptacles. A terminal screw has the bare wire wrapped clockwise around the screw and the screw is tightened to make the connection. Another type of terminal has a screw with a plate. The bare wire fits under the plate and the screw tightens the plate against the wire. A bare wire inserts into a hole on a quick-connect terminal. A spring clip makes the connection and prevents the wire from pulling out.