Things You'll Need
Certain appliances, as well as service-panel subpanels, require 240-volt circuit breakers, also known as double-pole breakers. Double-pole breakers are twice as wide as standard breakers and attach to both of the 120-volt hot-bus bars in the service panel. In addition, these heavy-duty breakers have two incoming wires rather than the single wire for standard breakers. Adding a circuit to a service panel is a relatively simple home improvement project.
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Turn off the power to the service panel at the main breakers. These main breakers are labeled and normally found at the top of the service panel.
Remove the panel covering the breakers by unscrewing the fasteners at the corners.
Make sure there is room for another double-pole breaker. You need two horizontally adjacent slots. Depending on the layout of the existing breakers, you may have to move a breaker by unclipping it from the bus bar. If there are no slots available, you will need an electrician to install a subpanel.
Remove one of the round knock-out plates on the outside of the service panel. The wires running into the box pass through these holes. Install a cable connector in the hole. The locknut of the connector is affixed on the inside of the panel.
Feed the wires from the heavy-duty circuit through the cable connector and tighten the clamp screws. Make sure you feed enough cable to reach the circuit breaker. Once the cable is tightly installed, tighten the locknut.
Connect the white wire from the cable to the neutral bus bar, which you can identify by the other circuits' neutral wire connections. Connect the bare copper or green ground wire to the neutral bus bar or the ground bar if present.
Insert the black and red wires into the double-pole breaker and tighten the set screws.
Snap the breaker into place on the hot-bus bars. It should slip into place without being forced.
Pry off the slot covers on the panel covering where the breakers will pass through. Reinstall the panel.Turn on the main breakers.