Things You'll Need
The NEMA L6-30R is one of the receptacles approved by the National Electrical Manufacturers Association in the U.S. This type of female plug is a two-pole, three-wire, 250-volt, 30-amp locking receptacle. It has two hot wires and one ground wire; it is designed to lock onto a NEMA L6-30P male plug by twisting the plug once it is inserted into the receptacle.
Turn off power to the circuit that you are working on by flipping the switch of the main circuit breaker inside the electrical panel to its "Off" position. The main circuit breaker is typically placed in the uppermost position inside the panel, and has the greatest amperage among all breakers.
Pull the electrical wires gently out of the outlet, and strip off 1/2 inch from the covering of each wire with the use of a wire stripper. The NEMA L6-30R receptacle uses a red (hot), black (hot) and green or bare wire (ground) to complete its circuit.
Hold the NEMA L6-30R receptacle and view the terminal screws behind it. Wrap the red wire clockwise around the brass terminal screw; tighten the connection with a screwdriver. Wrap the black wire clockwise around the brass terminal screw; tighten the connection. Wrap the green or bare wire clockwise around the green terminal screw; tighten the connection.
Fold the wires and tuck them inside the outlet box. Push the receptacle onto the wall; fasten it using the screws supplied with the receptacle. Cover the receptacle with its faceplate and fasten the holding screws.
Flip the switch of the main circuit breaker to its "On" position. Connect a 220-volt appliance with a L6-30P plug into the L6-30R outlet. Test the connection by turning on the appliance.