Published In June 2001
The common cry heard these days from electrical contractors is, “We need to save energy costs.” With the blackouts in California, the increase in fuel prices, and the incentive for reduced energy usage, it is time to revisit the advantages of compact fluorescent lamps (CFLs) in downlighting applications. CFL downlights using four-pin lamps on electronic ballasts are the most energy efficient. Improved luminaire designs, system flexibility, and lower maintenance costs are other reasons to look carefully at CFL downlights. Energy efficiency The greatest selling point for installing CFL downlights is they may directly replace a design using incandescent downlights. A compact fluorescent lamp requires one quarter of the energy and provides light output comparable to an incandescent. This results in immediate energy savings of over 70 percent. In addition, the CFL has a rated life of 10,000 hours, as compared to 1,000 hours of an incandescent lamp. Keep these facts in mind when comparing luminaire prices. The lower maintenance costs of CFL downlights will offset the higher initial purchase price. The energy efficiency story continues in two other areas. Since there is a direct relationship between watts and BTUs, the lower operating temperatures of CFL downlights result in reduced air conditioning loads. And because of lower power consumption, you can have more CFL fixtures on one circuit as opposed to the higher draw and inrush current of incandescents. Most CFL installations will require fewer circuits. Luminaire design tradeoffs Whether you are replacing incandescent luminaires or designing a new CFL downlight project, the luminaire design and light distribution should be considered. Perhaps the most important thing to remember is the larger lamp size of the CFL, compared to an incandescent, makes it harder to produce a downlight with a small, precise beam pattern. Typically, CFL downlights are used for ambient or general lighting, wall washing, and emergency lighting. They should not be used for accent lighting. CFL downlights are commonly offered in horizontal or vertical lamp models. Horizontal lamp fixtures are available with one, two, or three lamps and have a lower overall height. These work well in areas with shallow ceiling plenums. Horizontal-lamped downlights produce medium to wide beam spreads in normal ceiling applications. Because of the lamp position, horizontal CFL fixtures usually have better cutoff and produce less glare than vertical lamp downlights. Most vertical lamp downlights are designed for a single lamp, although two-lamp fixtures are available. Obviously their overall height is greater. Vertical CFL luminaires typically offer narrow and medium beam spreads for more concentrated light distribution and higher ceiling applications. Most, if not all, U.S. manufacturers of CFL downlights use electronic ballasts. These ballasts are designed to optimally drive the lamp, which results in high luminous efficacy, improved lamp life, and excellent power quality. However, CFL downlights with an electronic ballast will emit radio frequency interference (RFI) and electromagnetic interference (EMI). Although the CFL electronic ballast meets FCC nonconsumer specifications, it may not be suitable for residential or some commercial installations. Another consideration when choosing a CFL downlight is the reflector material. The anodizing process that produces the layers of a finished reflector surface can cause iridescence. Iridescence occurs when the reflector separates the wavelengths in the light the CFL’s rare earth phosphors produce. This is often described as a “ rainbow-like effect.” This can detract from the appearance of the downlight when looking along the ceiling. This iridescence will not effect the photometric performance and can be controlled by the thickness of the finish coating. Higher-quality reflectors usually do not exhibit this effect. System flexibility Unlike twin- and quad-tube lamps, four-pin triple-tube lamps of different wattages have similar electrical characteristics. This means the same ballast can drive different wattage lamps. Energy Savings, an electronic ballast manufacturer, produces a universal voltage (120 through 277) ballast that can operate either a 26W, 32W, or 42W triple-tube lamp. If you have installed luminaires with 32W triple-tube lamps and the customer complains the lighting is too bright, you can quickly and easily replace the lamps with 26W triple tubes. This will lower the light level without changing the ballast or fixture. The one disadvantage to earlier CF lamps was that, unlike incandescent lamps, they could not be readily dimmed. A relatively new technological upgrade to CFL downlights is simple digital dimming that can be installed without a complex hard-wired control system. Where once analog dimming limited the user, digital dimming has eliminated the restriction of one level of lighting for all luminaires on the same circuit. Some digital dimming systems also have the capability to program up to 12 different lighting scenes. This offers your customers the ability to easily change illumination levels in multipurpose areas. Some systems can also program and control not only CFL lamps, but also line and low-voltage incandescent and linear fluorescent, all in the same room. CFL lamps are available in a large range of color temperatures, from 2,700 to 5,000K. Adaptability of mixing warm color temperatures with incandescent lamps or the cool color temperatures of linear fluorescent and high-intensity discharge (HID) lamps makes the CFL a great complementary lamp. Specifier or contractor luminaires? CFL downlights are available as contractor- or specifier-grade luminaires. Compared to the contractor grade, the specifier luminaires will have deeper “throats” to accommodate thicker ceilings, self-framing trims, and channel-bar hangers (instead of bar-hangers), and better quality and construction. These generally have reflectors designed for specific applications and low brightness with good lamp image cutoff. The advantages of energy consumption, efficiency, and lower maintenance mean that designers, specifiers, and electrical contractors should always consider CFL downlights. They can be used in a variety of applications such as retail stores, motels, schools, offices, and churches with great results. Who could argue that CFL downlights aren’t a great benefit to energy-conscious design? FLETCHER, a lighting designer from England, is currently an application engineer for Ruud Lighting, Racine Wis. He can be reached at yazi_fletcher@Ruudlighting.com.