Double pole breakers are used to supply 220 to 240 volts power from the panel box to the appliance. A 30-amp breaker actually has two switches, one for each leg of power. Each leg comes from the secondary connections of the transformer supplying the building's panel. A 30-amp breaker is able to supply a total of 7.2 kilowatts or 5.76 kilowatts according to the maximum appliance limit. A 30-amp breaker uses 10-gauge wire and for many applications a 4-conductor cable with red, black, white and ground wires. Wiring one into a panel box is relatively simple, but does require working around energised connections.
Remove the panel box mounting screws. Turn the main breaker off. Use a flashlight as necessary to see. With hammer and punch, remove a 3/4-inch knockout. Put in the cable clamp and tighten the retaining nut with the hammer and punch on a nut tab.
Insert the 10-gauge, 4-conductor cable through the cable clamp. Pull enough wire through the clamp to leave a 3-foot tail. Tighten the two cable clamp screws until the clamp is snug.
Strip the cable's outer sheathing. Route the ground wire to the ground wire bus. Make neat angles with the needle-nose pliers. Cut the wire to length with the cable cutters and insert the wire into the ground lug bus. Tighten the wire lug.
Route the neutral, white wire to the neutral bus using neat angles. Cut the wire to length and strip about 1/2-inch insulation with the wire strippers. Insert the wire into the neutral bus and tighten the neutral bus lug.
Identify the adjacent spaces to mount the 30-amp breaker. It will take two spaces in the breaker box. Route the red and black cable wires to these two spaces with neat angles. Cut the wire to length and strip about 1/2-inch insulation from the end of each wire. Insert the wires into the breaker lugs and tighten.
Remove the respective breaker space covers from the cover panel with pliers. Reinstall the cover on the panel box with the mounting screws. Turn the main breaker on and test the appliance on the new breaker.
Make sure the breaker matches the panel box brand. Cutler-hammer, GE, Square-D, etc., all use different breaker configurations. Some motor applications can use a different load calculation for wire requirements. Check the specific wiring code for these applications. Some appliances, such as a hot water heater, can use a 2-conductor cable with ground. Check the specific wiring code for these applications.
Always wear safety glasses. Be extremely careful around energised circuits. Electricity can kill. Electrical panels cannot be de-energised by turning off the main breaker. There is power present. If not familiar with working around energised circuits, call an licensed electrician.