Thursday, 13 November 2008 21:51
What does “T8” mean?
The “T” designation in fluorescent lamp nomenclature stands for tubular; the shape of the lamp. The number immediately following the T gives the diameter of the lamp in eighths of an inch. A T12 lamp is therefore twelve-eighths of an inch, or one-and-one-half inches in diameter. A T8 lamp is eight-eighths of an inch, or one inch in diameter. A T5 lamp is five-eighths of an inch in diameter.
What are the color characteristics of T8 and T5 lamps?
T8 and T5 lamps achieve both improved color rendering and high efficacy by employing rare-earth phosphors. The correlated color temperature (CCT) and color-rendering index (CRI) of the lamps is controlled by varying the selection of phosphors. The CRI of T8 and T5 lamps can be specified from 70 to as high as the mid-90’s. Every lamp manufacturer has a product coding system denoting CRI, which may require a catalog to decipher. For great lighting quality, specify a CRI of at least 80.
Do T8 lamps require a special ballast or fixture?
T8 lamps require electronic ballast specifically designed to operate lamps at a lower current than T12 lamps. Whenever T12 lamps are replaced with T8 lamps, the ballast must also be replaced. When you install electronic ballast for optimum light quality and efficiency; electronic ballasts don’t flicker or hum, and they use less power! T12, T10, and T8 lamps can all use the medium bi-pin base, which allows T8, and T10 lamps to fit into the same luminaires as T12 lamps of the same length. T5 lamps have a different base, and are shorter than T8s, so new lumenaires are needed.
Electronic ballasts operate fluorescent lamps at much higher frequencies (20KHz and up) than the standard 60 Hz at which magnetic ballasts operate lamps. Because of the common .88 ballast factor, many electronic types of ballast provide a slight reduction in light output while using significantly less power compared to magnetic ballasts, which generally have a ballast factor of .94. Electronic ballasts with higher ballast factors (as high as 1.2) produce more light. Electronic ballasts offer lots of advantages, such as no flicker, less heat, much less noise, and the ability to operate as many as four lamps on a single ballast; some offer dimming, soft start, and better power quality characteristics as well.
How long do T8 lamps last?
T8 lamps have the same 24,000-hour + rated lamp life as standard T12 lamps. Frequent on/off cycles can reduce fluorescent lamp life. Using programmed start or dimming ballasts can increase lamp life to as much as 30,000 hours. T8 lamps also exhibit a slower decline in light output over time, relative to T12 lamps. At 40 percent of their rated life, standard T12 lamps only produce about 80 percent of their initial rated light output, compared to about 90 percent for T8 lamps.
What are the savings from using T8 lamps?
T8 lamps used with electronic ballasts will typically use about 32% less energy than the same lumenaires with T12 and magnetic ballasts. Additional savings are possible if a lighting re-design indicates the use of reflectors and delamping, or fewer lumenaires. Longer lamp life and less lumen depreciation mean lower maintenance costs. Worker productivity increases with light quality improvements.
Click and enter your phone number for immediate assistance