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Lighting Tips & Resources

What is a compact fluorescent lamp?


The compact fluorescent lamp is a fairly conventional, although somewhat miniaturized fluorescent tube packaged with an integral ballast (either iron/magnetic or electronic) in a standard screw base that can be installed into nearly any table lamp or lighting fixture.

There are two types of compact fluorescent lamps:
1. Modular, with bulbs and ballasts that can be separated and replaced separately.
2. Integral, with ballasts that are permanently built into the bulb and discarded with the bulb when the bulb burns out.

These types are being heavily promoted as energy savings alternatives to incandescent lamps. They also have a much longer life - usually 7500 to 10,000 hours, and sometimes up to 20,000 hours - compared to 750 to 1000 hours for a standard incandescent.

When choosing to switch to compact fluorescent lamps, there are a few things to be aware of:
- They are often physically larger than the incandescent bulbs they replace and simply may not fit the lamp or fixture conveniently or at all.
- The elongated or circular shape may result in a less optimal lighting pattern.
- Compact fluorescent lamps usually do not produce full light output until they warm up for a minute or two. A few models require about three minutes to fully warm up and produce as little as 20-25 percent of their full light output when first started.
- Many models have light output claims that are only achieved at the optimum operating temperature and/or in some optimum burning position that achieves an optimum internal temperature. Many light output claims are outright exaggerated, often by about 15 percent and in a few extreme cases by 25 percent.
- The light is usually slightly different from that of incandescents, often slightly less yellow and slightly more pink, more purple, or more blue. The spectral output of these lamps is usually concentrated in a few specific bands of the spectrum, and this can slightly distort color rendering. Any color difference from other nearby lamps may be undesirable and result in less than pleasing contrast with ordinary lamps and ceiling fixtures. Newer models have been addressing this issue.
- Some types (usually iron ballasts) may produce an annoying 120 Hz (or 100 Hz) flicker.
- Ordinary dimmers cannot be used with compact fluorescents.
- Like other fluorescents, operation at cold temperatures (under around 50 degrees F) may cause reduced light output or erratic operation. Some models work fairly well down to about 35 degrees F, others may get noticeably dim below 60 degrees F. The optimum temperature range of a particular lamp may vary with burning position, generally preferring cooler temperatures if operated base-down. Compact fluorescents may also not like excessive heat. Some ballasts are unreliable in ambient temperatures much over 120 degrees F. This is sometimes a problem in enclosed or recessed ceiling fixtures if heat in the fixture builds up.
- There may be an audible buzz from the ballast, usually from iron ballasts.
- They may produce Radio Frequency Interference (RFI).

tipBEST FOR EXTENDED USE
Like other fluorescent lamps, compact fluorescent lamps should only be used where they are left on (on an average) at least 15 minutes, preferably at least a half hour, once they are turned on. Starting a fluorescent lamp causes wear and tear on the electrodes (except for a few specific exceptions such as RF electrodeless lamps).


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