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Tips for Using Compact Fluorescent Lamps

Compact fluorescent lamps come in several sizes and configurations and can be energy-efficient solutions for many lighting situations. Check out the following applications for tips on how to best use CFLs.

Recessed Downlighting

Compact fluorescent lights (CFLs) come in several sizes and configurations. They can be applied nearly anywhere that incandescent sources are used for general area lighting, including ceiling downlights. For greatest success in using CFLs in downlight applications, keep the following pointers in mind:

  • A primary concern about retrofitting CFLs into fixtures that were designed for incandescent lamps is that the light distributions will not be the same. When choosing a CFL replacement, be careful to use a lamp that has a very similar size, shape, and lumen output to the original incandescent.
  • Recessed downlight fixtures are candidates for retrofit kits that use CFLs. The specific kit will depend on ceiling height, desired lumen output, and desired light distribution.
  • Most CFLs do not produce enough light for high-ceiling (above 12 feet) ambient lighting applications.
  • CFLs are not appropriate for certain situations, such as accent lighting or glittery retail display, where tight beam spread or sparkle is needed.
  • Standard CFLs cannot be installed on existing dimming circuits. Only CFLs with dimming electronic ballasts can be dimmed.
  • Relamping horizontal-lamp downlights may be difficult because of the limited space at the top of the downlight. Most horizontal-lamp downlights have openings opposite the lamp end to make relamping easier.
  • Rule of Thumb: To determine the approximate equivalent incandescent lamp watts, multiply the compact fluorescent watts by 3.5.
  • Be aware that some CFL-ballast systems don't start at cold temperatures. The starting temperature specifications vary and are available from the manufacturers. Light output may be temporarily reduced in cold temperature areas until the lamps have time to warm up.
  • The standard twin and quad lamps were designed to operate on normal or low power factor magnetic ballasts. CFLs with electronic ballasts have high power factors. For maximum energy savings choose high power factor ballasts.

Outdoor Lighting

When considering the use of compact fluorescent lighting (CFL) in outdoor locations, three primary issues should be addressed:

Lamp Starting

  • Compact fluorescent lamps are designed to start and operate within a specific temperature range. This temperature range affects how efficiently (and if at all) a CFL will light. At low temperatures, it is more difficult for the ballast that is driving the lamp to create and maintain the gas arc necessary to produce illumination. Changes in ballast and lamp components can increase a lamp's ability to start at lower temperatures.
  • The local low-temperature conditions need to be considered when choosing a CFL product. The local temperature conditions may be such that most lamp products will easily light at the lowest expected temperature.
  • It may be that your area has occasional temperature dips for a day or weeks. It is important to consider whether the potential for a few days without CFL lights is acceptable in your situation. If it is not, then choose a lamp with a low enough temperature starting range to cover all possibilities in your area.
  • Many currently available CFL products are rated to start at 0 degrees F. The Defense Logistics Agency offers products with starting ratings at -20 degrees F.

Lamp Output

  • The same temperature range that affects how a CFL will light also affects the ultimate light output of the lamp. At low temperatures, the lamp provides less light. In these cases, it is more difficult for the ballast that is driving the lamp to produce maximum illumination.
  • Many CFL products have a rating that relates the percentage of full light output at a specific outdoor temperature. These ratings are typically based on what is called "lamp wall temperature." The Defense Logistics Agency offers CFL products that specify a 50% or greater lighting output at 0 degrees F.
  • If the specific amount of light output is critical to your installation, then this must be carefully considered. It may be necessary to install higher wattage or additional lamps to cover cold periods. A better option might be additional lamps that are switched separately and only used during cold times of the year.
  • In most exterior applications, there is only a requirement for a reasonable amount of light to avoid hazards. In these cases, designing for a specific light level at the ultimate worst temperature case may be unnecessary; each case must be considered on its own merits.
  • The use of an enclosed fixture will help maintain higher "lamp wall temperature" and therefore higher levels of light output in colder weather. The enclosure provides an air space that serves as an insulator to the outside temperature, which helps maintain proper operating temperature. The enclosure also helps the lamp maintain warmer temperatures by greatly reducing any wind chill effect. The lens of the enclosed fixture will reduce the light output a little but is beneficial in terms of overall light output and protection of the lamp itself.

Applicability

  • Applicability is generally a subjective judgment. However, the low-temperature conditions and nature of exterior spaces present definite potential problems that must be considered.
  • Extreme low-temperature conditions or high wind chill potential can mean that a CFL may not be suited for outdoor use. If low light output and starting trouble are likely to occur often, it may be more practical to stay with an incandescent product for that location.
  • As with all fluorescent light products, the ability to provide a concentrated narrow beam of light is greatly reduced because the fluorescent lamp does not have a single point source of the light produced. If an outdoor light is to provide a concentrated beam of light that must travel great distances (such as a spotlight on a reader board at some distance), then an incandescent product is likely a better choice. However, this does not create any problems for the vast majority of cases where general doorway, façade, or walkway illumination is required.