Things You'll Need
Plastic/metal electrical box
Before you begin installing a 20-amp switch, make sure that the breaker box has enough space for a 20-amp circuit breaker. A 20-amp circuit breaker requires 12-2 gauge wiring. Therefore, you can't just remove an old breaker and replace it with a 20 amp unless it has a 12-2 gauge wire. Precautions must be taken to prevent electrical shock and to ensure safety in the wiring. If you are unsure of your capability of completing this job accurately, you should not attempt it. Using the correct size wire is vital.
Turn off the power at the circuit breaker box.
Find a location for the new 20-amp outlet.
Run 12-gauge wire from the circuit breaker to the new outlet location. Pull out 1 foot of wire through the back of the electrical box. Refer to the reference link near the bottom of this page for instructions on installing a 20-amp breaker.
Secure the electrical box with the hardware provided. Push the bulk of the 12-2 wire back into the wall, leaving about 2 inches out to work with.
Strip about 1/4 inch of the insulation from the white wire and the black wire. Use the pair of needle-nose pliers to form a hook at the end of all three wires.
Connect the white neutral wire under the silver screw on either side of the receptacle. Facing the hook that you formed in the opposite direction that you are turning the screw will make this task easier and ensure a snug connection.
Connect the black hot wire under the gold screw on the opposite side of the neutral wire.
Carefully push the wire back into the wall, leaving about an inch in the electrical box. Fold the leftover wire to be placed behind the receptacle, being careful not to disconnect any wires.
Attach the receptacle to the electrical box with the hardware provided.
Install the face plate using the hardware provided.
Turn on the power and test the new outlet.
The proper size wire must be used in order to meet code and avoid a fire hazard.
Take all precautions necessary to insure your safety.