Hardwiring an Appliance

Most 120-volt appliances simply plug into standard receptacles. Some 240-volt appliances plug into special 240-volt receptacles. Other appliances -- those that use 240 volts and are stationary -- are hardwired, meaning that cable attaches directly to the circuit. Garbage disposers and dishwashers may be either plugged in or hardwired.

Shut off power to the circuit before installing any appliance. These are general directions for some typical installations. Consult the manufacturer's instructions before wiring -- wire colors and cable connections may vary.

Appliance disconnects
If you shut off a circuit breaker to work on a 240-volt appliance, another person may mistakenly flip the breaker on while you are doing the wiring, creating a very dangerous situation. That is why building codes may require a hardwired appliance to have a disconnect -- basically an on/off switch. The disconnect must be positioned within sight of the appliance. An alternative is to install a circuit breaker with a lockout feature, which allows you to lock the breaker shut to prevent an accident.

Checklist

Time
About 1 hour to make most connections once cable has been run

Tools
Screwdriver, flashlight, strippers, lineman's pliers, long-nose pliers

Skills
Stripping, splicing, and connecting wires to terminals

Prep
See that the new appliance does not overload the circuit. Remove the old appliance or run cable for a new appliance.

Materials
Appliance, wire nuts, electrician's tape

Under the sink, a split and switched receptacle can provide an always-hot plug for a hot-water dispenser and a switched plug for the garbage disposer. Some codes may require the disposer to be hardwired, in which case a separate, switched junction box is needed (shown).

Codes may require a dishwasher to be on a dedicated circuit. Some models plug into receptacles, but most are hardwired. Provide a cable that can reach to the front of the dishwasher. Slide the dishwasher into the space and make the plumbing connections. Open the dishwasher's junction box and splice wires to the dishwasher's leads. Replace the junction box cover.

A water heater requires a dedicated 240-volt circuit. Check the unit's amperage rating and make sure the circuit can handle at least 120 percent of the rating. For most homes, a 30-amp circuit with 10/2 cable is sufficient. Because of the heat the unit generates, use Greenfield or armored cable rather than NM cable. Remove the cover plate, splice the wires (note that a neutral is not required), and replace the cover plate.

Garbage disposers are sold without cords so they can be wired directly to a junction box (hardwiring) or to an appliance cord with a plug. Install armored cable (shown), or buy a cord that can handle the disposer's amperage rating. Splice the wires to the disposer first. Install it under the sink. Then hardwire or plug the disposer into a switched receptacle. A disposer should not be on a light circuit, or lights will dim when it starts.

An electric cooktop or wall-mounted oven requires a 120/240-volt circuit -- 120 volts to power lights and timer, 240 volts for the heating elements. A cooktop and an oven can be wired to the same circuit. Run cable to a nearby junction box. An electric oven or cooktop usually has a short length of armored cable, called a whip. Clamp the whip to the junction box; make the splices. Make sure the wire and breaker are big enough for both.