Turn a switch on and it completes the circuit, letting electricity flow through it. Turn it off, and the circuit is broken; the switch creates a gap that stops the flow.
Essential switches
The most common household switch, a single-pole, has two terminals and simply turns power on or off.
A three-way switch has three terminals; a four-way has four. These are used to control a light from two or three locations, such as in a stairwell, at either end of a hallway, or in a large room with more than one entrance.
A dimmer switch (or rheostat) controls a light’s intensity. Usually you can replace any single-pole switch with a dimmer. However, buy a special fan or fluorescent dimmer switch to control a fan or a fluorescent light a standard dimmer will overheat and can burn out a fan motor or a fluorescent tube.
Special switches
In addition to the familiar toggle and rotary switches, specialty switches can do everything from turning on when you walk into a room to varying the speed of whole-house fans. You’ll also find special-duty switches that can be time-programmed or that let you know if a remote light is on or off. Decorative switches include styles that rock back and forth or slide up and down rather than toggling.
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single-pole switch has two terminals and a toggle labeled ON and OFF. Always connect two hot wires to it, not two neutrals.
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three-way switch has three terminals, and its toggle is not marked for on or off.
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rotary dimmer switch is the most common type. Some styles look like toggle switches.
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sliding dimmer with an on/off toggle “remembers” how bright you left the light the last time it was on.
Two ways to wire a switch
End-line switch wiring: If power goes to the fixture first and then to the switch, you have “end-line” wiring. Only one cable enters the box, coming from the fixture. Here, the white wire is taped or painted black to indicate that it is hot.
Power through switch: With “through wiring,” power enters the switch box. The feed wire (the hot wire coming from the service panel) runs to the switch before it goes to the fixture. Two cables enter the box-one coming from power and one going to the fixture. The neutrals are spliced, and a hot wire connects to each terminal.
Single-Pole Switches
An electrical switch controls the flow of power in an electrical circuit. It provides an open circuit in the OFF position and acts as a short, or closed, circuit in the ON position. A switch having two screw terminals is known as a single-pole switch; it can control a circuit from one location only. Most residential switches are single-pole switches. Power is connected to one side of the switch at all times. When the switch is on, electricity flows form the wire attached to the powered screw terminal, through the switch, and into the fixture or appliance wiring connected to the other screw terminal. If the switch is at the end of a circuit, power will flow through the black hot wire and return through the white neutral wire, taped black to classify it as hot. (Neutral current in the white wire equals that in the black wire; in the ON position, either wire can cause an electric shock.) If the switch is in the middle or a run, two black hot wires connect to the switch and the two white neutral wires are spliced together with a wire connector in the switch box. Splice together the bare copper grounding wires, and then pigtail them to the green grounding screw on the switch and in the box, if it is metal.
Three-Way Switches
Like a single-pole switch, a three-way switch controls the flow of power in an electrical circuit, but from two different locations instead of just one. This type of switch is useful, for example, when you want to be able to turn on a stairway light from either the tip to bottom of the stairway, or a detached garage light from either the house or the garage. Such switching requires special three-conductor or three-way switch cable with ground. This type of cable is usually round, rather than flat like conventional nonmetallic (NM) cable, and it contains an additional, insulated conductor- a red wire.
Three-way switches also differ form single-pole switches in that they have three screw terminals instead of two: a COM terminal (dark screw), and two traveler screws to connect wires that run between switches. The switch also has a grounding screw. The switch does not have either an ON or an OFF marked position because the COM terminal alternated the connection between two different switch locations, allowing either position to potentially close the circuit.
You must consider three different cables when wiring a three-way switch: the feeder cable, the fixture cable, and the three-wire cable. The typical wiring method is to run the two-wire hot feeder cable into the first switch box, and then the three-way switch cable between the first and the second switch box. You can then run a second two-wire fixture cable between the second switch box and the fixture box. An alternative method is to run the hot feeder into one switch box; then run the three-way switch cable from the first switch box to the light fixture and then to the second switch box. Either method initially requires that you run the hot feeder to a switch box. It’s also possible to run power first to the light fixture, but this method is not preferred because it’s more difficult to troubleshoot if there’s a problem in the circuit.
Four-Way Switches
A four-way switch can be connected between tow three-way switches to allow you to control a light from three different locations. A four-way switch is installed in line or “series” with the travelers between the two three-way switches. A three-way cable should be run from the first three-way to the four-way switch and from the second three-way switch to the four-way switch. The red and black wires from the first switch connect to the brass-color screws, and the black and red wires from the second switch connect to the dark- or copper-color screws. The white neutral conductor is carried all the way through all switches. Pigtail the grounding wires to the green grounding screw inside the metal switch box.
Dimmer Switches
A dimmer switch allows you to regulate luminosity, or brightness, of light emanating from a light fixture-either to set a mood or conserve energy. Dimmer switches can be single-pole or three-way switches. In a three-way configuration, only the dimmer switch regulates brightness, while the paired toggle switch merely turns the fixture on or off. Though not commonly used, dimmer switches are also available for fluorescent lighting.
Dimmer switches are controlled by a solid-state device within the switch that alternately turns the current on and off as many a s120 times per second. By restricting the flow of current, the switch dims the light. The longer the current is off, the dimmer the light. Standard dimmer switches are rated for 600 watts.
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