How to Install a 20 Amp 240 Volt Circuit
- 1). Turn off the main breaker. Remove the inner cover from main breaker panel. Don't remove the smaller panel that protects the main breaker. Feed the cable from your basement, crawl space or attic, as appropriate, into the main panel. If you have enough room, feed the cable through one of the existing holes.
- 2). Cut an opening in the wall where the receptacle will be located. Feed the other end of the cable through the wall and then through the opening that will hold the receptacle. Strip the cable's outer sheath back about 6 inches using the utility knife. Be careful not to cut the inner wires. Strip the ends of the individual wires about 1/2 inch from the end, using the wire stripper.
- 3). Attach the wires to the receptacle. The two colored wires connect to the gold terminals. The white wire connects to the clear or neutral terminal, and the green or bare wire connects to the green terminal. Tighten all wire connections, making sure no part of the bare wire touches any other wire. Mount the receptacle to the wall and install a cover plate.
- 4). Install the breaker in the electrical panel. Hook it onto the center bar, holding it at about a 45-degree angle, and swing it down until it snaps in place. Cut the outer sheath of the cable as above and strip the ends of the wires. Attach the white wire to the neutral bar, where other white wires are attached. Connect the ground wire to the ground bar and then connect the two colored wires to the breaker. Tighten all connections and replace the inner panel cover.
- 5). Turn on the new breaker and the main breaker. Use the voltmeter to confirm that the receptacle has 240 volts between the two hot terminals. Check the voltage from each of the hot terminals to the neutral terminal. The voltage should be 120 volts. Repeat this for the hot terminals to the ground terminal. You should get 120 volts again.
Source...