How to Wire a Garage Disposal

Switch off the circuit breaker that controls the garbage disposal wiring from the main electrical box. Locate the wiring for the disposal beneath the sink cabinet. If the wires are contained in an electrical box with a cover, remove the cover with a Phillips screwdriver to reveal the wires. Hold a no-touch electrical current tester near the wires. Continue if the tester does not detect current in the wires.

Remove the retaining screws from the bottom of the disposal, using a nut driver or Phillips screwdriver, depending on the brand. Insert the wires from under the cabinet through the stress relief clamp on the underside of the disposal. Pull enough wire through the clamp to make the electrical connections to the disposal wiring. Don't tighten the clamp yet.

Strip ½ inch of insulation from the ends of the wires from under the cabinet and the wires on the underside of the disposal, using wire strippers.

Twist the bare ends of the white wire from the disposal to the white wire from the electrical box under the sink cabinet. Twist a wire nut -- usually included with the disposal -- onto the bare wires, twisting clockwise until tight. Place a couple of wraps of black electrical tape around the nut and approximately 1/2 inch down on the wires. Connect the black wire from the disposal and the black wire from the electrical box in the same fashion.

Loosen the green ground screw on the underside of the disposal with a Phillips screwdriver. Wrap the bare ground wire from the electrical box around the screw and tighten to secure the wire.

Tighten the stress relief clamp on the underside of the disposal with a Phillips screwdriver. Carefully push the connected wires into the cavity on the underside of the disposal. Replace the cover and tighten the retaining screws.

Turn the circuit breaker back on and test the operation of the disposal.