Air compressors accumulate and release high-pressure air for use in a various applications, and are commonly powered by a 220- to 240-volt AC motor. Many people still refer to AC voltage from a utility company as 110 volts and 220 volts, but standard voltage has been increased to 120 volts and 240 volts, respectively. Depending on how close you are to a transformer, the actual voltage in the wires can range from 117 to 121 volts, and from 234 to 242 volts.
Turn off the main circuit breaker inside your electrical panel. The main circuit breaker is typically installed on the top of the panel, and has the highest ampere rating among all breakers. Remove the electrical panel cover using a screwdriver.
Mount a 240-volt self-contained surface mount outlet on a wall nearest to the compressor. Note that the amperage of the outlet must match the amperage required by the compressor manufacturer. Read the owner's manual of your 230-volt air compressor to determine the required amperage of all electrical components that should be installed in the circuit, such as circuit breaker, wires and outlets.
Run a black wire, a white wire and a green wire across the ceiling, and drop one end of each wire through an available conduit pipe above the electrical panel. Pull down the cable and cut using diagonal pliers when the wires reach the bottom of the panel. Run the other end of the wires down to the self-contained 240-volt outlet, and cut it once it reaches the outlet. Use cable staples every 12 inches to fasten the cable to the wall. Strip off 1/2 inch from the insulation at the tip of each wire with a wire stripper.
Unscrew the faceplate of the 240-volt outlet with a screwdriver to reveal the terminal screws behind the plate. Loosen the gold-colored terminal screws on each side of a 240-volt outlet using a screwdriver. Loosen the green terminal screw at the bottom of the outlet. Hook the black wire clockwise around a gold terminal screw on one side of the outlet. Hook the white wire clockwise around a gold terminal screw on the other side of the outlet. Wrap the bare or green wire around the green terminal screw, and tighten each screw to secure each connection.
Wrap electrical tape twice around the side of the outlet to cover the terminals. Wrap black electrical tape around the white wire to indicate that it is live. Tuck the wires gently in a zigzag manner into the outlet box. Mount the faceplate onto the outlet box using the screws supplied with the outlet.
Place a 240-volt circuit breaker in front of a vacant slot on the electrical panel board. Push down the breaker into the slot to engage the copper clips beneath it onto the metal bus bar. Never allow any part of your body to come in contact with any metal conductors inside the electrical panel.
Route the black and white wires running from the conduit pipe above the electrical panel to the terminal screws behind the 240-volt circuit breaker. Route the gray or bare wire to a vacant terminal screw on the ground bar. Cut the wires once they reach the terminal screws and strip off 1/2 inch of insulation from the tip of each wire using a wire stripper. Wrap a band of black electrical tape around the white wire to indicate that it is live.
Loosen an unoccupied terminal screw on the ground bar, and loosen the two terminal screws at the end of the 240-volt circuit breaker, using a screwdriver. Insert the stripped ends of the black and white wires into each slot under each terminal screw on the 240-volt circuit breaker in any order. Insert the stripped end of the gray or bare wire into the vacant terminal on the ground bar. Tighten the three terminal screws, and pull on each wire slightly to make sure its secure.
Replace the cover of the electrical panel, and turn on the main circuit breaker. Plug the compressor into the 240-volt outlet and turn it on to test the wiring.