When doing any type of outlet wiring, it's important to verify you're working within your local building codes. Some municipalities require this work to be done by a licensed electrician. Once you have checked the local code requirements, wiring a 220v outlet for a dryer or other appliance is similar to the common 120v household outlet, with a few key differences.
There are several gauges (sizes) of wire that are suitable for use with a 220v circuit. The key to selecting the correct gauge wiring is determining the amperage load of the device for which you are adding a receptacle. A clothes dryer uses a 30 amp 220v circuit, which would then require 10 gauge three conductor wires.
Step 2 - Position the Dryer Receptacle
For the purpose of this tutorial, we'll assume we're mounting the receptacle on a basement wall. In order to properly locate the receptacle, you will measure from the floor to a height of 48 inches. This will be the bottom of your receptacle. Drill pilot holes with a masonry bit and then mount the box against the wall with masonry screws.
Knock the top knockout from the receptacle and attach an offset fitting using a locknut. Measure the first section of the conduit and cut it with the hacksaw. Use the round file to remove any rough edges from the ends of the conduit and attach it to the offset fitting from the receptacle. Lock it in place with the set screw. Attach the conduit to the wall with conduit clamps and masonry screws within three feet of the receptacle, and then every 10 feet to the end of the run.
Make bends by using sweep fittings and continue running the conduit to the breaker panel. Use elbow fittings where the run may take many turns or that require long wires. The cover is removable on the elbow and will facilitate pulling of the cable.
It is very important here to shut OFF the Main Triple Pole Circuit Breaker of the electrical to avoid short circuits, getting an electric shock or injury, and even electrocution. But since this will remove all power to the house, install a battery-powered trouble light first to illuminate the area. Remove the cover and remove a knockout plug in the panel. Attach a set screw fitting to terminate the conduit into the panel.
Step 4 - Run the Wire
Unwind the fish tape and extend it through the conduit from the panel outward. Remove any elbow covers as necessary. Insert the wire through the loop at the end of the tape and secure it in place with electrical tape. Straighten any kinks in the wire and apply pulling lubricant to the taped end of the fish tape. Retrieve the wires through the conduit by pulling the fish tape slowly with steady pressure. Use extreme caution with the metal fish tape in the circuit panel, even if you believe the power to be off.
Step 5 - Connect the Circuit
On the dryer receptacle, attach the white wire to the center setscrew terminal. Connect the black and red wires to the other two set screw terminals and attach the green wire to the outlet box ground terminal. Place the receptacle in the box and attach the cover plate. With the main circuit breaker still off, connect the red and black circuit wires to the setscrew terminals on the 30 amp double pole circuit breaker. Connect the white wire to the neutral bus bar in the panel and the green wire to the grounding bus bar. Attach the breaker panel cover and turn on the main and the new circuit.
The only thing that remains to be done is a test of the circuit. This can be done with the circuit tester.