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Compact Fluorescent Lamp Basics

Written by Jack Brautigam

Compact fluorescent lamps are an energy-efficient option to common incandescent light bulbs. They also last much longer than incandescent bulbs. Compact fluorescents take advantage of folded-tube technology for compactness and come in a variety of sizes and shapes. They also use premium color phosphors to achieve color rendition comparable to incandescent lighting. Lamps come with both plug-in and screw-in bases, and ballasts are required for operation. This factsheet defines terms used to describe compact fluorescent lamps and lighting in general.

Lamps

• Lamp
  A light source; typically a bulb or tube. Twin Tube (or U Tube) .A compact fluorescent lamp with a single folded tube. Lengths range from 4" to 7".

• Quad Tube (or Double Twin Tube)
  A compact fluorescent lamp with two folded tubes or one double folded tube. A quad tube's advantage over a twin is that higher wattages are made possible in a smaller package.

• Capsule Lamp
  A capsule-shaped light source. With compact fluorescents, an integral lamp and ballast unit with screw-in base and capsule type enclosure providing the appearance of an incandescent source.Tubular, globe, or other shaped enclosures may be used.

• Reflector Lamp (or R Lamp)
  A directional light source using a highly reflective surface to focus light into a beam. Reflector enclosures designed for fluorescent quad tubes can be substituted for standard incandescent reflector spot and flood lights. Integral and modular assemblies are available.

• PL Lamp
  A compact fluorescent with pin base. A modular or hard wired ballast is needed for operation.

• SL Lamp
  A compact fluorescent capsule lamp.

• Pin Base
  Most fluorescent lamps have pins for plugging them into a fixture. The number of pins (usually 2 or 4) and arrangement of the pins varies considerably. Compact fluorescent lamps are an exception; many are available with screw-in bases for use in standard sockets.

Ballasts

An electromagnetic or electronic device used to start and maintain required circuit conditions (voltage and current) for fluorescent and other types of lamps. Ballasts consume a small amount of energy. For example, a typical 13 watt lamp with ballast actually uses 16 watts. Ballasts may be integral, modular, or hard-wired.

• Integral Ballast
  A ballast used together with a compact fluorescent lamp as a single screw-in unit. When the lamp fails, the entire unit is thrown away.

• Modular Ballast
  A ballast with screw-in base used as an adapter for compact fluorescents with pin bases. When the lamp fails, only the lamp needs to be replaced. Modular ballasts are designed to last from 2 to 5 lamp changes.

• Adapter
  A modular ballast.

• Hard-Wired Ballast
  A ballast (magnetic or electronic) that is separate from the lamp, but is built directly into a fixture for permanent installations. While this ballast is generally long-lived, it can only be replaced by rewiring.

• Electronic Ballast
  A ballast designed to operate at high frequency (e.g. 25,000 hertz) using electronic components resulting in improved energy efficiency compared to electromagnetic ballasts. Electronic ballasts are lighter in weight and perform better at low temperatures than standard electromagnetic ballasts. They also offer instant starting with no flicker. On the down side, costs are higher for electronic ballasts.

General Terms

• Input Watts
  The total watts consumed by a light fixture including lamp(s) and ballast(s).

• Fixture (or Luminaire)
  A complete lighting unit including one or more lamps, ballasts (if needed), and parts to position the lamps, distribute light, and connect lamps to a power source. The number of fixtures designed explicitly for compact fluorescent lamps is limited, but new designs are appearing continually.

• Lumen (lm)
  A unit of light output. For example, a standard 60 watt incandescent light bulb produces about 850 lumens of light. Compact fluorescents produce this same amount of light using only 15 to 18 watts.

• Lumens Per Watt
  A measure of the energy efficiency of light output, or lamp efficacy. A typical compact fluorescent lamp produces 40 to 60 lumens/watt compared to incandescent lamps at only 8 to 18lumens/watt.

• Footcandle (fc)
  A unit of light on an object or illuminance equivalent to one lumen uniformly striking a surface one square foot in area. Available light (measured in foot-candles) not only depends on the lumen output of a lamp, but on the location of the lamp with respect to the viewing surface.

• Color Rendition
  The effect of a light source on the color of objects. For example, daylight makes all colors appear vivid, though most electric lighting will accent some colors while washing out others. Most compact fluorescents have color rendering superior to standard cool white tubes making skin tones appear more natural.

• Color Temperature
  The warmth or coolness of a light source. Warm sources appear more yellow and have low temperatures (e.g. 3,000K). Cool sources appear more white or blue and have high temperatures (e.g. 4,000K). All light sources have a color temperature that defines their color appearance. Most compact fluorescent lamps have temperatures of 2,700K, equivalent to incandescent lighting.

Washington State University Cooperative Extension

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