Many window-mount air conditioners, air compressors and residential welders plug into a Nema 6-30R. A Nema 6-30R connects to a 240-volt 30-amp electrical circuit with 10-gauge, or larger, three-strand wire. Two wire strands supply the electricity to the Nema 6-30R, and the third provides a ground connection. A Nema 6-30R has two straight, horizontally aligned prongs above its ground prong. The horizontally aligned prongs supply the voltage. A standard-size wall-mounted electrical box holds a single Nema 6-30R, and only one appliance can plug into it at a time.
Turn off the Nema 6-30R outlet's circuit breaker. The circuit breaker that controls a Nema 6-30R should have a 30-amp rating.
Remove 1/2 inch of the coating from each insulated wire in the outlet's electrical box. In most cases, two of the three wires use an insulated covering, but in some cases all three wires have an insulating covering.
Examine the back of the Nema 6-30R. Its three wire terminals use slotted screws, located on the back of the outlet's housing, to secure the wires in place. Each wire enters the outlet through the holes in the side of the outlet's housing, located below each terminal screw. Two wire terminals face the bottom of the outlet and the third faces the top.
Loosen the Nema 6-30R's terminal screws with a flat-head screwdriver. Do not remove the screws.
Push the end of the ground wire, either the uninsulated wire or the wire with green insulation, into the single hole located on the top of the outlet's housing. Tighten the screw with the flat-head screwdriver.
Push the black wire into the Nema 6-30R housing's bottom right-side hole. Tighten the terminal screw with the flat-head screwdriver.
Push the white wire into the Nema 6-30R housing's lift-side hole. Tighten the terminal screw with the flat-head screwdriver.