Gain Complete Control Over Your Home Lighting by Wiring a Light with Two Switches
Installing a light fixture in a room which will be operated by two switches instead of one is a useful skill that can help you control the lighting in your home. The process is somewhat more involved than when using a single switch, due to the increased number of wires and connections involved. If you are ever at all unsure of the process or worried that you may be doing something wrong, it is best to consult a qualified electrician.
Before beginning the process, make sure that both the plastic switch boxes and the lightbox are securely fixed to studs or joists, and that a Romex cable has been fed through them. In the lightbox there should be a cable which runs up from the main power source. Regardless of whether the current is 15 amp or 20 amp, the cable will be either 14/2 or 12/2 Romex. There should be a two-wire cable, containing a black, white, and bare wire, between the lightbox and the first switch box.
From the first switch box to the second you should use a length of three-wire Romex. This cable contains three wires and a grounded wire, which are generally coloured red, black, white, and bare. Make sure that you allow for at least 6 inches of cable to protrude from each box to give yourself plenty of room to work. It’s a good idea to have more cable than is necessary, as you can always stuff the extra back through the box when wiring is complete.
Safety first, so once you begin the wiring process you should make sure that the circuit you are working on is switched off. To check that this is the case use a voltage meter. After doing this, strip away the insulation from each end of the Romex cable in the lightbox to free the three wires. Stripping an inch of the insulation from each of the two black and two white wires should then be done on both the cable coming from the source, and the one going to the first switch box. The ground wire doesn’t need to be stripped.
Continue by connecting the white wire from your source to the white wire or silver screw on the light fixture. Twist the ground wires from both ends and fasten them with wirenut. Take the white wire leading to the first switch, wrap a piece of black electrical tape around it, and then twist it with the black wire from the source. Secure the connection using a second wirenut. Where the black wire leading to the first switch is concerned, nothing else needs to be done there at this time.
A total of 5 wires—2 white wires, 2 black wires and 1 red wire—need to be stripped in the first switch box. This includes attaching the white wire you had previously marked at the lightbox end with black tape, to the lower brass screw on the right side of the first switch. The black wire from the same box should then be connected to the black wire that is leading to the second switch box. Connect the two ground wires using a fourth wire nut.
Mark the other end of the white wire leading to the second switch box with black tape too, and then connect it to the left side of the switch. The red wire should be attached to the top brass screw on the right side. In the second switch box, mark the other end of the white wire and connect it to the left side of the switch. Connect the red wire to the top screw on the right side of the switch, the ground wire to the screw on the switch box, and the black wire to the bottom brass screw on the right side.
Finally, go back to the first switch box and connect the black wire leading to it with the light fixture. Turn the circuit back on and check that everything is working as intended. Both switches should now be able to successfully turn the light on and off. If this is not the case, ensure your connections are secured and check again. When you are satisfied, stuff the wires in the boxes, secure them inside, and attach the faceplates.