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Compact Fluorescent Lamps (CFL)

By: Jonathan Z. Kremer

January 2009

By now everyone has heard of the Compact Fluorescent Lamps (CFL). They have been in the news, on and off, for the last couple of years and are being heavily promoted as energy savings alternatives to incandescent lamps. Being they have a much longer life (usually 7500-10,000+ hours) compared to a standard incandescent (750 to 1000 hours), many places around the world are in the process of banning incandescent light bulbs in favor of CFL and other energy saving type lamps.

But what is a CFL and how does it work? The CFL is actually a miniaturized version of a common fluorescent tube, packaged with an internal ballast, sporting a standard screw base, which can be installed as a replacement for the incandescent bulb, into nearly any common lighting fixture. To reduce the space that this fluorescent tube takes up, manufactures either bend the tube in a zigzag, or in a circular cork screw shape. The inside of this tube is coated with a fluorite coating and filled with small amount of mercury vapor. There is a small heating filament at each end of the tube that is used to warm the mercury into a vapor. When electric current flows through this vapor the atoms get excited and give off ultraviolet light. When the ultraviolet light is absorbed by the fluorite coating, it fluorescences, which in turn causes it to give off visible light. The light output is regulated by an electronic ballast built into be base of the bulb.

Although CFLs have a lot of advantages they are not without a down side. Some of the disadvantages include:

  1. The cost of a CFL is still a bit high -usually 8-10 times the price of a regular incandescent bulb.
  2. They are usually physically larger than incandescent bulbs, so sometimes they may not fit in certain fixtures.
  3. The advertised light output is usually exaggerated to as much as 15% or more, and the lamps do not produce full light output until they warm up (1-3 minutes).
  4. Like standard fluorescents, CFLs are usually temperamental to high and low temperatures, as well as dampness.
  5. They may produce Radio Frequency Interference (RFI).
  6. Ordinary dimmers cannot be used with standard CFLs.
  7. Some people consider the small amount of mercury in the bulb to be a potential health hazard should the lamp be broken.

Nonetheless, CFLs are definitely a desirable alternative to incandescent bulbs in most cases. They are about 300-400% more efficient than incandescent light bulbs, and they last 5-8 times longer. They give off significantly less heat, which make them a much less fire risk.

Like other fluorescent lamps, CFLs are best used in places where once they are put on, are left on for at least 15 minutes or more. The reason is that CFLs can take up to 3 minutes to warm-up and reach the point where they operate most efficiently and brightly. Lighting a fluorescent lamp of any sort, not only causes wear and tear on the electrodes, but uses more energy for the start-up, than what would otherwise be used during normal operation. Therefore frequently switching CFLs on and off will not only shorten their life, but significantly cut into your financial benefits (energy & life of lamp). Naturally, the ideal place to use a CFL is a location where the light will stay on for a while.

When using a CFL, never try to forcefully twist the CFL into a light socket by its tubes. Always screw and unscrew the lamp by its base.

It is a good idea to check and see if the CFL you are buying has a energy star logo. This means that it has met certain testing specification, which includes among other things minimum efficiency and longevity standards.

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