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Wiring devices.

Article Excerpt
Wires and cable form circuits to carry electricity through a building. Wiring devices described here are used to control current flow and provide access points so electricity can be used to power appliances and lights.

Switches

A switch controls power to lights and devices by turning off the hot side of the circuit. Selection depends on design and load capacity.

Conventional Switches

A conventional switch makes or breaks contact when a mechanically connected tumbler or toggle bridges or breaks the line contacts in the switch.

A single-pole switch is simplest and most frequently used in the home, controlling current on one circuit from one point. It features two terminal screws.

Double-pole switches have four terminal screws.

A three-way switch controls one circuit from two separate points, such as a garage light that can be turned on or off from the house or the garage.

Four-way switches are used in connection with three-way switches to control one circuit from three or more points.

Single-pole and three-way switches are available with lighted handles that glow in the dark.

Dimmer Switches

Dimmer switches control the amount of current in a lighting circuit, allowing the user to control the degree of light from off to full capacity.

Some dimmers control the amount of voltage going to the lamp, increasing or reducing the amount of light given off. Other dimmers control a portion of each alternating current cycle applied to the lamp. This means a solid state dimmer turns the light off and on approximately 120 times per second. The on-off rate has no noticeable effect on the life of the bulb or on the eves of persons in the room.

One undesirable side effect of this on off cycle is interference on AM radios. Some dimmers have radio/TV filters and printed circuitry. There are table lamp dimmers and dimmers that wire parallel into the lamp cord. In addition, use of a dimmer will cause some light bulbs to "hum." The sound is created from the turning on and off of the A.C. sine wave. The rapid switching causes the tungsten filament to resonate. Filament hum is typical with inexpensive lamps that are commonly installed in new construction. The hum can be greatly reduced by upgrading to a lamp with a heavier filament.

It is also normal for a dimmer to get warm during operation, which is why dimmers are built with a heat sink. If the load is not over the wattage rating of the dimmer and is a proper load for which the dimmer is designed to control, the dimmer does not need to he replaced.

There are several styles of wall dimmer switches available. The most popular include a push on-off/dial-to-dim type, a rotary full-range type, a slide type and a toggle type that offers flail-range control but uses toggle motion instead of a dial.

Dinners also come in single-pole or three-way construction. If two, three-way switches are involved, only one of them can he a dimmer. Otherwise, the setting will not work, although some toggle dimmers allow two three-way switches to be used.

An air gap switch is built into all dimmers as a safety feature to ensure that power can be removed to the output--this is a UL requirement.

Specialty Switches

Rocker switch--used in place of a standard wall switch, it is activated with a pushbutton mechanism. Useful near a doorway or area where hands might be lull or for appearance and for range hood and appliances.

Delayed-action switch--circuit remains active for a few minutes after switch is thrown. Useful in garage or breezeway, allowing individual to get into the house before light goes out.

Programmable memory switch--set to go on and off at specific times for security or safety purposes.

Photoelectric switch--operates by light striking cell. Usually used on yard lights. Daylight turns circuit off; it goes back on at dusk. Circuit usually has a delay device to prevent passing headlights from turning light off.

Motion switch--turns the light on as you enter the room. Used for both convenience and security. Can be used to replace existing wall switches.

Illuminated switch--is available in two types. One has a small light that is on when the switch is off so it can be easily found; these are usually used at entrances to rooms and in hallways. Pilot light switches are on when the light...