How to Hardwire Appliances
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. We'll provide tips and tricks for hardwiring five common appliances: a garbage disposer, a dishwasher, an electric water heater, and an electric cooktop. Some garbage disposers and dishwashers may be either plugged in or hardwired, so consult your device's instruction manual before starting.
Once a cable has been run and/or the old appliance has been removed, you can expect to spend an hour making most connections. Make sure you know how to strip, splice, and connect wires to terminals. Before you start wiring, check that the new appliance does not overload the circuit.
What You Need
- Lineman's pliers
- Long-nose pliers
- Wire nuts
- Electrician's tape
Before You Begin: Safety Tips
Before you do anything else, shut off power to the circuit. When working at such high voltages, an accidental shock could be deadly.
Some building codes require a hardwired appliance to have a disconnect—basically an on/off switch. This disconnect must be positioned within sight of the appliance. Some circuit breakers also have a lockout feature, which allows you to lock the breaker shut to prevent an accident. The last thing you want is to shut off a circuit breaker to work on a 240-volt appliance, then have another person mistakenly flip the breaker on while you are doing the wiring.
It's also important that you understand these are general directions for some typical installations. Still consult the manufacturer's instructions before wiring—wire colors and cable connections may vary.
How to Wire a Garbage Disposal
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 disposal. Some codes may require the disposal to be hardwired, in which case a separate, switched junction box is needed.
Garbage disposals 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, or buy a cord that can handle the disposal's amperage rating. Splice the wires to the disposal first. Install it under the sink. Then hardwire or plug the disposal into a switched receptacle. A disposal should not be on a light circuit, or lights will dim when it starts.
How to Wire a Dishwasher
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.
How to Wire an Electric Water Heater
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.
How to Wire an Electric Cooktop
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.