Technologies > COMPACT FLUORESCENT DOWNLIGHTS

 

Introduction: Compact fluorescent lamps (CFLs) have become the standard for commercial application recessed downlights over the past 10 years, with incandescent and halogen declining in use and low-wattage metal halide (MH) carving out a significant share of its own, according to some fixture manufacturers. They report that CFLs are by and large the dominant light source in low- and medium-height ceiling general downlighting applications.

Incandescent Downlights: Incandescent/halogen lamps offer the advantages of low initial cost, good color rendition, economical dimming with a familiar cool-to-warm color shift, point source lighting, and very compact lamps in low wattages.

Disadvantages include inefficiency, short lamp life, and heat. A typical incandescent lamp converts only a small fraction of its electrical input into light; the rest is dissipated largely as heat.

CFL downlights: CFLs are energy-efficient, long-life sources that produce shadow-free illumination, practical dimming for some applications, minimum heat output, and a range of color temperatures.

CFLs, however, are often not well suited for higher mounting heights or focused accenting. In addition, dimmable CFLs do not shift to a warmer color temperature when dimmed as incandescents do.

Recent developments include:

• CFL downlights using higher-wattage lamps are starting to replace MH where longer throws and or higher light levels are required.
• Demand is increasing for long-life electrodeless CFL downlighting for difficult-to-service locations such as over stairwells and escalators.

Low-wattage MH downlights: Low-wattage MH downlights are energy-efficient, offer good color rendering and long service life, and are more of a specular light source than fluorescents. The optimal combination is a ceramic metal halide (CMH) lamp powered by an electronic ballast; this combination extends lamp life, improves color consistency, reduces color shift, eliminates end-of-life cycling, can result in more compact fixtures, and can enable more fixtures to be connected to each circuit. CMH downlighting can even be more cost/energy-efficient than CFL downlights in medium ceiling heights because fewer, more optically efficient, higher-lumen, wider distribution downlights can be used versus CFLs.

However, instant restrike, dimming and battery backup are not yet practical for most applications, and these fixtures typically pose a higher initial cost. In addition, even color-optimal CMH lamps are as yet not as strong as incandescent lamps in the red component, which can be an important consideration in color-critical applications such as retail and display lighting.

Recent developments include:

• For difficult-to-reach fixtures, some manufacturers are offering two-lamp MH downlights, in which the lamps take turns operating, effectively doubling the time between relampings.

LED Downlights: White LEDs have created considerable excitement in the lighting industry and have potential for commercial downlights. In particular, they can be desirable for niche applications where their advantages—including long life, vibration resistance, small size, low forward heat projection and/or ability to fine tune color temperature—outweigh the disadvantages.

However, because of the disadvantages, LEDs for downlights are not yet economically viable for most applications. These disadvantages include lower light output, high cost, difficulty dissipating heat, and low color quality and consistency.

Retrofits: CFLs can be as much as 80 percent more efficient and can last more than 10 times longer than incandescent lamps. For instance, a 26W CFL can replace a 100W incandescent lamp for a savings of 75 percent. CFLs have an average CRI of 82 and come in a wide range of color temperatures.

The CFL can be plug-in (separate from the ballast, plugs into a socket using pins) or self-ballasted.

When the CFL is plug-in, it does not have an integral ballast and features 2 or 4 pins on its base for plugging into the socket. Be sure to match the CFL to the right socket for proper operation. Also note that 2-pin lamps run on magnetic ballasts and cannot be dimmed, while 4-pin lamps run on electronic ballasts and can be dimmed if the ballast has that capability.

When the CFL is self-ballasted, the lamp and ballast come together in a single unit with a screw-in base for direct replacement of incandescent lamps. Self-ballasted CFLs may also feature an integrated glass globe or a reflector to diffuse (soften) or direct the lamp’s light output.

Screw-in CFLs are often not recognized by utility rebate programs because once expired, the CFL can be easily “snapped back” to a higher-wattage incandescent.

Similarly, Standard 90.1-2001 recognizes incandescent fixtures as the maximum wattage of the fixture, so screw-in CFL replacement of incandescent lamps does not generate load savings that are recognized by Standard 90.1-2001. Therefore, in existing installations, a retrofit fixture may be needed to replace the entire incandescent fixture with one optimally designed for use with plug-in CFLs.

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