FOR DISCUSSION ONLY —— FOR DISCUSSION ONLY —— FOR DISCUSSION ONLY —— FOR DISCUSSION ONLY
The problem: you want to add an indoor light fixture and don’t know where to begin.
Background: you will need to know how much current the light fixture will draw. If you are wanting to add a switch to turn on or off your 50,000 Christmas tree lights, do yourself a favor and seek professional assistance. This is geared towards the person who is wanting to add a common fixture that will contain a single 100 watt light bulb or a small fluorescent fixture.
You may use either 12 or 14 gauge wire for this task. TIP: the smaller the gauge number, the larger the wire and the more current it can draw. There is a wide variety of wire on the market so take a moment to look it over closely before you purchase it. Recall this is an indoor job so you most likely will not need the additional expense of outdoor wire (this may not apply if you are wiring a fountain or anything near water). Most of the wire I have purchased over the years has been copper. If you look at the wire, you will see that there are actually three wires in one. One will be black, one will be white, and one will probably be bare. The convention in the U.S. for the black wire to contain power, the white wire to be neutral, and the bare wire to be the ground.
Running the wire through walls can be tedious and dangerous. TIP: You may have existing live wires or plumbing hidden within the walls you are working on. Your local code may require you to enclose the entire wire inside conduit.
Supplies:
The solution: work backwards to minimize the amount of time that you will need to have your circuit turned off. Start with the fixture. Most lighting fixtures require a separate electrical box. It may be metal or plastic. I prefer 4 inch square metal ones for light fixtures. It has to be connected to something. If your fixture is going in a ceiling, you will have to locate the studs and attach the box to one. Often, the studs will not run precisely where you want to place the box. Cut your 2x4 and place it between the studs. Nail or screw (I use screws in the ceiling to help with the weight) it in place so that it becomes a part of the structure. TIP: think about where you want the light fixture to be. If you attach the box to the bottom of a stud, the light fixture will be connected to the box and you will probably have a gap between the light and the ceiling. If you recess the box into the ceiling, you can make the fixture flush with the ceiling. You are responsible to make certain that the switch can be firmly attached to the structure. An old fashioned porcelain light switch can be attached directly to the box. A large chandelier may require cable, chains, lag bolts, or other means to secure the weight of the fixture.
You will also need a box wherever you want the switch. A switch will not carry much weight so I feel comfortable using plastic for these. Attach this box to a stud (I use nails as their is no weight). If you run conduit, do that now. Be very careful when drilling through walls. Regardless of whether you use conduit or not, you will need punch out the access holes to your box and attach the wire stabilizers. Run your wire from box to box and leave about nine inches of slack on both sides before cutting. If you are running exposed wire (no conduit) you should use wire staples to keep it in place. Take a few minutes and straighten out the wire. Do not leave any kinks or twists in the wire. The wire staples should keep the wire in place but not cut the wire on place undue pressure on the insulation. Make certain that the path of the wire will not interfere with anything. TIP: don't wrap it around a chimney—too hot. Watch out for heating ducts. Open your eyes, look around, and think about keeping your wire safe and dry.
Once the wire has been run and stablized at the light fixture box, remove about six inches of the outer insulation. Remove about an inch of insulation from both the black and white wires. Look at the light fixture. You will probably see two screws and off to the side a small green one. Take the black wire and wrap it around one of the screws and then do the same with the white. It usually doesn't matter which wire goes to which screw but I would look the fixture over carefully and read any directions that came with it. You will also see a green screw somewhere on the fixture. Attach the bare ground wire to it. Once these wires are all attached, you may fasten the light fixture to the box. This end is now complete.
Strip the wires at your switch box the same as you did for the light box. You will need a power line. You may run a new circuit of your main power source or tap into an existing circuit. TIP: if you don’t know what you are doing, ask a licensed electrician or run a new circuit. Check the code for your location. Run the wire has been run between the light switch and the power souce like you did before. NOTE: turn off the power before opening any live power box or going any further. Use your tester to verify that it is off. NEVER work on a live circuit. TIP: for twenty years I always used my tester to make certain that my power was turned off. One day, I checked a line that I had just turned off and found that my cheap tester lit up. I was shocked (surprised actually) to see that the line was still live. It happens on occasion and you simply might not get a second chance when working around electricity.
With the power turned off, attach the white wires with wire nuts inside the light switch box. Take both of the black wires and attach one to each screw on the switch. Attach the ground cable to the switch. You may now push everything back in the box and cover the switch with a faceplate. Connect the power line to your power source inside of a junction box or at the main power source. Connect black to black, white to white, and bare ground to bare ground.
Finally the switch box. It is simple. The white wires are connected with wire nuts and pushed back into the box. Each of the screws on the switch should have a black wire atttached to it. The bare ground wires should be be connected to the green screw on the switch. Many switches now provide the option of just pushing the wire into a hole and you don't even have to mess with the screws. The screws are typically on the side and the holes I refer to are on the bottom. Those with the holes also often have a strip guide molded into the plastic to show you how much of the insulation should be removed. This can save a lot of time but you only want to stick the wires in the holes when you are certain that you have everything correctly in place. Once everything is assembled, push all of the wires back into the box and place the cover back on. Now you merely have to turn the circuit back on and test to make cerain that it works as expected.