In most modern kitchens, lighting is the one thing that tends to suffer most, and in a room full of knives, dimness isn't exactly what you want to have. Good lighting can instantaneously transform a normally dark kitchen into one that's safer, more efficient and just plain better looking. Installing under-cabinet lights is one of the most effective ways of achieving these results. And while it may take a little more time, hard wiring the cabinet lights will provide you with longer lasting, more dependable illumination than using poorly constructed battery-operated lights.
Turn off the circuit breaker that powers the outlet where you will be working. Use the voltage tester to make sure the power is off to the outlet.
Unscrew and remove the outlet's cover plate. Unscrew the two screws that secure the outlet to the wall box and pull the outlet out. Test the wires again for voltage, and disconnect the wires from the outlet if they are not carrying voltage.
Hold the double-gang old work box face-first up against the existing wall box. Make sure that the corners meet and then outline the double gang box on the wall using the pencil. Cut out the outlined area using the keyhole saw.
Remove the existing wall box by prying it away from the stud with a screwdriver or flat pry bar. Make sure the outlet's wires don't fall down inside the wall.
Drill a hole through the wall (using the drill and a 1.27 cm [1/2-inch] spade bit) directly below the base of the cabinet and right above where you will be installing the switch.
Feed the NM cable through the drilled hole and reach your hand up inside the wall where you expanded the hole for the double gang box. You should be able to grab the cable. Once you grab it, pull it down and through the lower access hole.
NM cable stands for non-metallic cable. This is the sheathed cable that houses the individual black, white and ground wires for running the circuit. It is often called "Romex."
Disassemble the under cabinet fixture and hold its housing up against the underside of the cabinet where you are planning on installing it. Slide it forward so it is butted up against the cabinet's front edge. Secure it to the underside of the cabinet using the screws that were provided with the fixture.
Tap out the knockout located at the rear of the fixture housing using a flathead screwdriver and a hammer. Insert the threaded nipple of a NM connector through the knockout hole and secure it in place with its locknut. Before tightening the locknut down, position the NM connector so the clamp screws are facing downward. Loosen the two clamp screws.
Cut the NM cable so you have enough to work with (about 30 cm [12 inches] of cable should be available from both the bottom access hole and from where the cable will be entering the fixture). Slide the cable through the NM connector until the cable is tight up against the underside of the cabinet, then tighten the cable clamps down.
Strip the sheathing away from the NM cable that's on the inside of the fixture. This is best done by slicing the sheath with a sharp knife and then pulling it apart. Cut away the excess outer sheath and the paper insulation so only the black, white and ground wires are in the fixture.
Insert the existing circuit for the outlet and the new line for the cabinet lights into the old-work double-gang box and set the box inside the hole you cut in the wall. Make it level and tighten the two screws (one in each corner) to engage the wings that will hold it in place.
Remove the sheathing from the NM cable in the wall box.
Cut two 15 cm (6-inch) lengths of black and ground wire and one 15 cm (6-inch) length of white wire, and strip 2 cm (3/4-inch) of insulation from both ends of all of them using the wire strippers.
Connect one of the lengths of black wire to the dark-coloured, line-side terminals on the GFCI outlet that you removed earlier. Connect the length of white wire to the silver, line-side terminal on the GFCI, and connect one of the lengths of ground wire to the GFCI's ground screw.
If the GFCI outlet was feeding other outlets, then it would have had a black and white wire connected to the load side when you disconnected it. If that was the case, connect the black wire (in the wall box) that travels to the next outlet to the dark-coloured, load-side terminal, and the white wire to the silver load-side terminal.
This will leave you with the main feed line (a black, white and ground) and the cable that's heading to the fixture inside the wall box (also a black, white and ground).
Take the second set of 15 cm (6-inch) lengths of black and ground wire and connect the ground wire to the ground screw on the switch, and the black wire to the line side terminal on the switch.
Twist all of the ground wires (the three in the wall box, the one from the GFCI and the one from the switch) together and secure them with a large wire connector. Push the ground wires as deep into the box as possible.
Twist the white wire from the GFCI to the three white wires in the wall box and secure them together using a wire connector.
Twist the black wire from the GFCI, the black wire from the switch and the black wire from the main feed circuit together and secure them using a wire connector. There should only be one black wire left in the wall box (the one that's going to the fixture). Connect it to the remaining screw on the switch.
Wrap both the GFCI and the switch terminals with electrical tape and secure them both to the wall box with the screws provided, and install the cover plate.
Connect the black wire in the fixture housing to the black wire on the fixture's socket bar using a wire connector. Connect the white wire in the fixture housing to the white wire on the fixture's socket bar using a wire connector, and connect the ground wire to the fixture's green ground screw.
Screw the socket bar in place using the provided screws and install the fluorescent tube and plastic lens cover.
Turn the circuit breaker back on and flip the switch to see your newly brightened kitchen.
For adding additional fixtures, a second knockout will have to be removed from the original fixture, outfitted with a NM connector, and have a NM cable fed from the first fixture to the second. Connections are made black to black, white to white, and ground screw to ground screw.
Always test a circuit that you know is working before you test the circuit you are going to be working on. This is to ensure the tester is functioning properly.
Troubleshooting a circuit often means that you will have to be testing live wires. If you are afraid or unsure of your ability to work with live electricity, please call an electrician to perform this job.