A 240-volt circuit is typically a dedicated circuit that provides an outlet for a stove, dryer, kiln or other high-voltage appliance. The circuit is usually wired during construction, but a gas stove is sometimes replaced with an electric one. The national code calls for grounded receptacles with four-prong outlets. Dedicated household circuits are not shared between appliances or used to run power to the receptacles and lights in any room. This limits the 240-volt wiring to one cable that runs from the breaker box to the 240-volt outlet.
- Skill level:
Things you need
- 50-amp breaker
- 6-3 cable
- Utility knife
- 4-prong 240V outlet
- Fish tape
- Electrical tape
- Slotted screwdriver
- Phillips screwdriver
- Junction box
- Mud ring
Open the breaker panel and shut off the main power switch. This is usually a larger breaker switch located over the rows of breakers, but it may be a uniform-size switch installed along the row. In either case, it will be labelled "Main."
Remove the screws holding the panel cover to the breaker box with a slotted screwdriver. Pull the cover off the box.
Cut the jacket of a 6-3 electrical cable 10 inches long at one end with a utility knife. Strip 5/8 inch of insulation off the red, black and white wires.
Loosen a screw terminal on the ground bus bar inside the service panel with a slotted screwdriver. The ground bus has a row of terminals connecting bare copper, or green, insulated wires. Push the bare copper wire from the 6-3 cable into the terminal and firmly tighten the screw. Put the white wire from your cable into a terminal on the neutral bus bar, which holds the other white neutral wires. Tighten that terminal securely.
Loosen the terminal screws on a 50-amp double-breaker switch with a slotted screwdriver. Put the red wire from the cable into one of the terminal clamps and the black wire into the other. The red and black are both hot wires that can go into either terminal. Tighten the terminal screws firmly. Clip the front end of the breaker switch that holds the wires onto the mounting bar and push the clamps at the back end over the hot bus bar.
Secure the other end of the cable to the hooked end of a fish tape with electrical tape. Push the fish tape up through a cable port in the top of the breaker box. Push far enough for the end to reach the attic or the attic crawl space. Retrieve the end of the fish tape in the attic area and carry it to the wall where the receptacle will be installed. Push it down the wall to the location of the 240-volt outlet.
Pull the fish tape through the hole in the wall for the outlet. Remove the electrical tape and cut 8 inches lengthwise down the jacket. Strip 5/8 inch from each of the three insulated wires. Push the stripped wires and the bare copper wire through a cable port into a junction box. Pull the 240-volt wiring through the mud ring. Secure the ring to the front of the junction box with the included machine screws, using the appropriate screwdriver.
Secure the junction box to the wall stud on one side of the hole in the drywall by inserting the included wood screws through the two holes on that side of the box and tightening them with a Phillips screwdriver.
Loosen the terminal screws on the 240-volt receptacle with a slotted screwdriver. Insert the bare copper ground wire into the terminal clamp on the outlet socket marked "Ground" and firmly secure the terminal screw. Put the white wire into the terminal market "Neutral" and tighten its terminal screw. Put the red wire into one of the "Hot" terminals and the black wire into the other. Firmly tighten all terminal screws.
Push the 240-volt wiring into the junction box and secure the outlet to the mud ring with the mounting screws. Put the cover plate over the outlet and secure it with the included screws.
Pull the two metal knockout strips off the breaker panel cover over the newly installed double-breaker switch. Replace the holding screws on the breaker box cover and flip the main switch to restore power. Turn the new switches to the "On" position. Test the 240-volt circuit by plugging an appliance into the receptacle and turning it on.
Tips and warnings
- Do not work on an electric service panel, a 240-volt receptacle or 240-volt wiring without proper training and experience in electrical work.
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