Circuit breakers are automatic safety switches that interrupt the flow of electricity when the current exceeds the maximum safe amperage. Single-pole circuit breakers handle 105 to 125 volts. Double-pole circuit breakers handle 210 to 250 volts. Double-pole breakers utilize both sides (thus double pole) of the current from the power supplier. On the circuit breaker panel, 230-volt breakers are easy to identify because they occupy two slots instead of one.
Turn off the main circuit breaker. This shuts off current to the rest of the circuit breaker panel. Set up your work light to shine on the panel.
Remove the screws that hold the panel cover in place and set the panel cover aside. Note the two terminal lugs on the main circuit breaker that hold two very large wires. These terminals and wires are always hot. Do not touch them.
Install the new 230-volt breaker in the panel. Hook the two non-conducting tabs onto the panel's flange, then firmly press the breaker onto the tabs. The breaker will seat on the tabs and bus bars and be flush with the rest of the breakers in the panel.
Switch the new breaker to the "off" position. Tape the switch handles in place with white electrical tape if the circuit will not be activated immediately.
Remove a convenient knockout panel from the panel box and install a new cable bushing in the knockout hole. Bring the the cable for the new circuit into the panel box through the cable bushing. Note the amount of wire in the panel for the other circuits and plan on arranging the new wires the same way. Strip the sheathing from the cable once it is inside the box.
Attach the bare ground wire to the ground bus. Insert the wire into an empty slot and tighten the screw that holds it in place and makes the connection. Remove 3/4 of an inch of insulation from the white neutral wire and attach it to the neutral bus in the same way. In some circuit breaker panels, the neutral and ground buses are the same.
Strip 3/4 of an inch of wire from the two remaining colored wires. Insert the stripped ends into the terminal lugs on the new circuit breaker, one into each lug. Tighten the terminal screws. The wires must not be able to pull out.
Remove two knockouts from the panel cover to accommodate the new circuit breaker. Install the panel cover with the screws. Label the new circuit breaker inside the panel door. Turn on the main circuit breaker and you are ready to complete the wiring at the other end of the cable.