Some tips for wiring 240 volt outlets include obtaining the necessary permits, using a circuit breaker of 240 volts, using a deep and wide outlet box, connecting the ground wire, and grounding a metal outlet box. Also, use the appropriate cables for appliances that use 120 and 240 volts and those that use only 240 volts, and do not use the cable's neutral wire when outlets with three poles are used.
Before wiring a 240 volt outlet, obtain the required permits from the building department of your locality. Use an outlet box with three or four poles for wiring the outlet, and begin the wiring by installing a circuit breaker of 240 volts within the circuit panel.
Use an outlet box that is deep and wide enough to accommodate heavy cables that are folded back into it. If the box is made of metal, ground it too by connecting the cable's bare ground to the green-colored ground screw, and running a green-colored or bare wire with insulation to the outlet.
To connect the ground wire, push in the corresponding wire in the outlet's ground lug, and screw it in place. If the outlet has four poles, push in the neutral wire in the outlet's neutral lug. In outlets with three poles, snip the cable's neutral wire at the point where it enters the outlet box, and leave it without connecting.
If the appliance uses only 240 volts, use a cable with two wires, and if it uses both 120 and 240 volts, use a cable with three wires. In both cases, the cable should have an additional bare wire for making the ground connection.