Wiring Lighting: Lighting Types
Wiring Lighting: Incandescent Artificial lighting is the primary illumination we use to perform tasks. Lighting also provides ambient, or general, lighting and decorative, or accent, lighting. The quantity and quality of light produced will depend on the type of lightbulb you use. Incandescent, fluorescent, and high-intensity discharge bulbs (including mercury-vapor lamps) provide the three major sources of artificial light. A standard incandescent lightbulb produces light when electricity is passed through a thin wire, or filament. As a result of heating, the filament emits a visible light called incandescence. Incandescent lightbulbs come in a variety of shapes and styles to match fixtures that are freestanding, wall or ceiling mounted, or recessed. The term luminaire describes the entire assembly of lamp, fixture, housing, and attached electrical wires. Surface-mounted fixtures are usually installed on a ceiling or wall. They may use incandescent, fluorescent, or quartz halogen bulbs. Wall sconces, globe lights, above-vanity strip lighting, and ceiling fixtures are all examples of this kind of lighting. Surface-mounted lights are generally connected to lighting outlet boxes.
Wiring Lighting: Fluorescent In a fluorescent tube, electrical current jumps from an electrode at one end of the tube and flows through the tube to an electrode at the other end. This current flow causes mercury and argon gases in the tube to emit ultraviolet (UV) light, which is not visible to the human eye. To make the ultraviolet light visible, the tube is coated with a phosphor powder that glows, or fluoresces, when it is struck by the light. (See page 136.) When the fixture is turned off, the mercury/gas mixture within the tube does not conduct electricity. When power is first applied, several hundred volts are emitted from the ballast to initiate the release of electrical energy. Once this occurs, however, a much lower voltage is all that is required to maintain power usually less than 100 volts for fluorescent tubes under 30 watts and 100 to 175 volts for tubes of 30 watts or more. When the higher voltage breaks down the gas and current begins to flow through it, the gas emir, a great quantity of ultraviolet light but not much visible light. Only when the UV light hits the phosphor coating does the tube begin to glow. Different phosphors are used to achieve the light spectrum required for the fluorescent tube's intended designation—cool white, warm white, colored, or black light. Fluorescent bulbs are about two to four times more efficient at light production than incandescent bulbs. They also last a lot longer—10,000 to 20,000 hours vs. 900 to 1000 hours for a typical incandescent. However, this does not take into account the expense of replacing a fluorescent light ballast when one fails. Nevertheless, not all fluorescent bulbs require ballasts, and they are more energy-efficient than incandescents, providing two to four times more light per watt and using fewer watts than standard bulbs. They are also fairly maintenance-free. Whether you are adding new fixtures or repairing existing ones, you will use many of the basic wiring techniques learned earlier in this book—including the handling of wires, switches, receptacles, and other electrical devices—to complete these projects. Refer to these techniques as you proceed with your wiring lighting and always check with the local building or electrical inspector to determine what code requirements will govern your project. |