Changing a Light Switch
Replacing or upgrading a light switch is a simple and inexpensive DIY project.
Attach the switch box to a wall stud. The typical height is 42" from the floor to the bottom of the box. If multiple switches are used, gang the boxes together. Follow electrical code recommendations as to the box area required for the number of switches installed.
Refer to your wiring plan (Image 1) to determine the most efficient wiring route from fixture to fixture.
Use an auger bit or Forstner bit (Image 2) in a power drill to bore 1” holes for the wiring. A heavy duty right-angle drill makes it easier to work in tight spaces between the ceiling joists. This tool, called a Hole Hawg, is available at most rental centers.
For this installation, we are using 12-2 NM electrical cable. The 12 refers to the gauge, or thickness, of the individual wires, or conductors. The 2 indicates there are two insulated conductors (a bare or green-jacketed ground wire is also included). The NM stands for non-metallic, or plastic-jacketed, cable.
Pull the cable through the drilled holes, working from one end of the circuit to the other. When wiring a series of lights, run a single length of cable from one fixture location to the next, but leave plenty of excess wire to work with at each fixture.
Follow the "Rule of 8's" -- leave at least 8" of wire extending out past each junction box, use wire staples to attach the cable to the wood framing within 8" from the box, and fasten the cable within 8" from where it extends into the wall.
At each fixture’s attached junction box, remove a knockout tab with a screwdriver (Image 1) for each of the incoming, and outgoing, cables and pull the cables into the box. Secure the cables with box clamps.
Use a wire stripper to remove about 1/2" of insulation from the ends of all the black and white wires. In addition to the incoming and outgoing wires, each box will contain one black and one white fixture wire.
Connect the wires and secure them with wire nuts (Image 2). Connect the three black (hot) power wires together, the three white (common or neutral) wires together, and the ground wires to each other. Also attach the ground wires to the box’s green ground screw, if provided, or to another metal connection in the box.
Wrap electrical tape around each of the wire nuts to ensure that the wire splices won’t untwist.
When all of the fixtures have been wired, pull the cable from the first light fixture into the switch box and secure it with a box clamp. Pull the power wire from the main circuit into the box. (Make sure the power is shut off, and test the wires with a circuit tester to be safe.)
Strip the insulation from the wire ends and attach each of the black wires to a brass screw on the switch.
The white wires do not connect to the switch. Twist them together and secure the splice with a wire nut.
Connect the ground wires to each other and to the green ground screw on the switch.
Install bulbs in all of the light fixtures, restore the power and test the operation of the switch and fixtures.