Changing light switches in your home can be a daunting task if you don't understand what the task entails. Going from one light switch to two can easily be done as long as all the components are there and the right tools are at your disposal.
Assessment and Task Prep
Before tackling any wires and switches, it is extremely important to go to the breaker and turn off the power to whichever room you are working on. Once the electrical current is gone, it is safe to remove the light switch cover and see what you are working with. Before you begin, make sure you also have all the necessary tools, such as a screwdriver, wire stripper and a voltage tester. The wires found behind the socket cover can be either black, red, white, green or a simple copper wire.
Working in an organized fashion is the key to successfully installing the new switch. Gather all the white wires and tie them together so they do not interfere in the process. Bring forward all remaining wires. There should be black and copper or red and green wires left. There may be multiple copper or green wires, but you only need one of them to install the switch successfully. Lightly turn in the bundle of white wires back into the socket to keep them out of the way. Space can become limited within the socket so make sure not to push them in haphazardly or the switch cover will not fit into place.
Using your voltage tester, identify all the "hot" wires or lead wires and mark them so you remember which ones they are. In this situation of installing a double light switch, there should be two lead wires. Make sure to mark them both. The other black wires are load wires (there should also be two of them). There should only be one copper or green wire left – that is known as the ground wire.
To begin installing the wires on the new switch, make sure each wire is stripped 5/8 of an inch from the end. Proceed by turning the end of the wire to resemble a hook so it can slip around the bolt on the switch and stay in position. Before attaching any wires, locate the brass piece between the two black screws on the new switch and break it off using a screwdriver. This piece must be removed before attaching any wires, otherwise you will blow your breaker when you use the new switch.
Take one lead wire and hook it onto one black screw on the new switch and tighten the screw. Do the same for the other lead wire onto the second black screw, making sure to once again tighten the screw. Continue with the load wires, taking one and connecting it to the brass wire. Then, take the other and connect it to the opposing brass wire. Tighten both screws and finish by attached the copper or green wire to the green screw. Tighten firmly once again. Gently twist the new switch into the socket and secure it to the wall. Finish the project by placing the socket cover back on and fastening it into place.
The lights in your room should now be controlled individually through the new switch. Do not forget to turn back on your breaker for that room, otherwise the lights will not turn on. If the lights still do not turn on, call an electrician to make sure the switch was installed properly.
This process can also be completed if only one lead wire is found in the socket. The main difference in installation is to leave the brass piece between the black screws in place to ensure the connection between the black screws remains intact. The connect the lead wire to either black screw and secure it tightly.