Many homeowners are afraid to tackle simple electrical projects - and rightly so. Electrical projects can be intimidating. But jobs like light fixture replacements can be easy and safe. The following offers some basic information every homeowner can benefit from - nothing too scary.
When working with electricity always:
Remove the wall plate and switch mounting screws so the switch can be pulled from the wall and the wires exposed. Don’t touch any of the wires until you’ve confirmed they aren’t carrying electrical current.
In contemporary wiring, individual wires run in a sheathed cable. Two-wire with ground and three-wire with ground cables are available. Two-wire with ground cables have a black wire, a white wire and an uninsulated ground. Three-wire with ground cables have a black wire, a white wire, a red wire and an uninsulated ground. Older houses may have knob-and-tube (K&T) wiring-a two-wire system. With this system, individual wires are insulated with white or black treated fabric.
Regardless of the type of wiring in your home, the white wire is usually the neutral wire, the black wire is "hot," and the exposed copper wires are ground wires. The white wire is sometimes used as a hot wire because some wiring installations require it. In this case, the white wire should be coded black with paint or electrical tape. Note, however, that it is possible that whoever did the wiring may not have coded the wire. If a red wire is present, it should also be hot.
A switch is what opens or closes an electrical current to a light fixture, ceiling fan, garbage disposer or other electrical device. There are single-pole, three-way and multi-location switches, double switches and dimmer switches. Switches may be wired at the end or in the middle of a circuit.
If only a single cable enters the box (or one set of black and white wires), the fixture is at the end of the circuit. This is usually, but not always, the situation with ceiling light fixtures. If two cables enter the box (or two sets of black and white wires in older K&T installations), the fixture is in the middle of a circuit. A third cable (or set of black and white wires) may also enter the fixture, depending upon the installation. The placement of the fixture within the circuit affects how it is wired.
The black, or hot wires, are connected to the brass screw terminals on receptacles and switches. The neutral wires are connected to the silver terminals. Ground wires should not be ignored. They should be connected to each other, to the grounding screw terminals (painted green) on receptacles, and to grounding screws in metal electrical boxes when metal boxes are used.
Pigtail leads are short wires which are connected to terminals on receptacles or switches. The leads are then connected to the home wiring using plastic wire connectors. Codes in some areas require that pigtails be used on all standard receptacle connections. Always use pigtails when more than one wire must be connected to a single terminal.