designs using 2, 4-ft T8 lamps per 4-ft section. The high bulb wall brightness limits their use in direct applications in low ceiling height conditions due to discomfort glare Following the trend to fluorescent, T5HO lamps are being used in high ceiling applications, including high-bay industrial fixtures.

T8 lamps

Standard T8 lamps (See Figure 13.6)

T8 lamps (1" dia) were originally imported from Europe in the early 1980s. The lamps now used in the US are different than their European pre-heat cousins and there are improved models. T8s have been the lamps of choice (along with the high frequency electronic ballasts that drive them) for fluorescent upgrades for several years. T8 lamps are available in 2', 3', 4', and 5' lengths, at 17, 25, 32, and 40-w respectively. These lamps require ballasts that supply 265 ma. There are also two versions of 8' retrofit lamps at 59, or 86-w. U-tubes are available in the new 1 5/8" leg spacing and a retrofit U-tube that has 6" leg spacing that is used to replace 6" leg-spacing T12 U-tubes.

Recent advances in T8 lamps have been in improvements in color rendering and longer life. Extended performance T8 lamps have a life rating of 24,000 (at 3 hours per start)—20% longer than standard T8 lamps. These extended performance lamps operate on the same electronic ballasts designed to operate standard T8 lamps. Lumen maintenance is rated at 0.94 and it levels off after that. Lumen output is slightly higher at 3,000 lumens and CRI is improved to 8. Standard 3000K, 3500K and 4100K colors are provided.

Reduced-wattage T8 lamps

Sometimes called "energy-saving" T8 lamps, these lamps are available in 28 and 30-w vs. the standard 32-w models. They are designed to replace reduced-wattage, 34-w T12 lamps, when upgrading to electronic ballasts. They are recommended for use only on instant-start elec-

Figure 13.6 Some T8 Lamp Sizes (Source: Sylvania)

tronic ballasts to provide the higher open-circuit voltage required and they need to be operated above 60°F. In addition, they cost more than standard T8s, but they save about 6% over standard lamps, are TCLP compliant, and have high lumen maintenance (94%).

High-performance T8 lamps (See Table 13.13)

These high-lumen lamps (3,100 L) are part of a dedicated lamp/ballast system that can save about 19% over standard T8 systems with the same light output and twice the lamp life (on program-start ballasts) compared to standard instant-start T8 systems. They exhibit high lumen maintenance (95%) and high CRI (86).

Table 13.13 High-Performance TS System Watts (Source: Osram-Sylvania)

Number of Lamps

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