Easy Steps for Wiring Residential Electrical Outlets
While wiring wall switches can quickly get convoluted if you are, say, dealing with lights on multiple stair landings, wiring electrical outlets tend to be simpler and easier. Your job is to not rush and make sure you understand what color wire goes where on the new receptacle. You can check your finished work with an outlet tester to see how well you did.
Before You Start Wiring
You need to match the size of your outlet box to the job. If you are doing an end-of-circuit outlet involving 14-gauge wire on a 15-amp circuit, an 18-cubic-inch box -- the smallest size -- will work. If you have heavier 12-gauge on a 20-amp circuit, you may need to go up to a 20.4 or 22.5 cubic inch box -- the volume is stamped on the inside of the box. Putting in the wrong size is a common mistake for newbies, writes online electrician Dean Johnson, so discuss the sizes with the electrical inspector when you submit diagrams, if you are wiring new construction.
Always turn off the power to the circuit before working with any wiring or devices. Test the circuit with non-contact circuit tester and proceed only if the test confirms the power is off. Once you have the right size box and have fed the cable to it, you are almost ready to let the wiring begin. If you have just one cable entering the box, you are at the end of the run, and you have the easiest scenario possible. Connect the white wire to the silver terminal screw, the bare wire to the green grounding screw, and the black wire to a brass or gold terminal screw. If the electrical box is metal, include pigtails (short lengths of bare copper wire) that connect to the circuit ground wire, the receptacle's ground screw and the grounding screw on the box; join the wires with a plastic wire connector, or wire nut. Carefully fold the wires back into the box. Screw the outlet to the box, top and bottom. Screw the cover plate’s center screw to the outlet and restore power to the circuit.
If you have two cables entering the outlet, you are looking at a middle-of-the-run receptacle. The second cable continues on its way to additional outlets or other devices in the house. In this arrangement, the black wires still attach to the brass terminal screws, and the white wires to silver terminal screws. It doesn’t matter which screws, upper or lower, either cables’ wires attach to, provided the receptacle is standard; for a GFCI receptacle you have to be mindful of the "LOAD" and "LINE" terminals (follow the manufacturer's wiring diagram). Twist the bare wires and a pigtail together into a wire nut (including an additional pigtail to ground a metal box). Attach the pigtail to the green grounding screw.