How to Wire a 20-Amp Breaker

Open the cover on your main electrical panel and turn off the main breaker. Hold the inner panel with one hand while you remove the screws holding the panel in place. Carefully remove the panel cover using both hands.

Locate an unused position in the panel. If it is a 240-volt breaker, you will need a space with two adjacent openings. Locate the blank(s) on the inner cover where the breaker will be installed and remove the blank(s) so that the cover will not block the breaker.

Turn on the voltmeter and set it to a minimum of 240-volts a/c. Touch one of the attached probes to one of the existing breaker's terminal. Touch the other probe to the ground buss. If there is no voltage present, you can safely install the breaker.

Hook the breaker on the center bar in the panel while holding the breaker at a 45-degree angle. Lower the breaker onto the panel until it snaps in place.

Strip the end of the unused black or red wire(s) 1/2-inch from the end(s) and insert the wire(s)into the breaker's terminal(s). Tighten the screw(s) to secure the wire(s). The 120-volt breaker will have one wire to connect and the 240-volt breaker will have two wires.

Strip the end of the white (neutral) and green (ground) wires as above and attach them to the common buss-bar. This is a metal bar with several white and green wires connected to it. If the breaker is located in a main-panel, the neutral and ground wires will connect to the same buss-bar. If you are working in a sub-panel, the two buss-bars will be separate.

Replace the inner cover and turn on the main breaker. Turn on the new breaker and connect a device to an outlet controlled by the breaker. Confirm that the device works and the breaker does not activate.