Lighting Research Center Lighting Research Center
    Volume 6 Issue 1
July 2002    
How can T5 lamps be used with direct/indirect pendant luminaires?

Pendant luminaires with direct/indirect (including indirect and semi-indirect) luminous intensity distributions are another popular application of T5 lamps (Figure 17-1). Luminaire manufacturers aggressively market these direct/indirect luminaires in a variety of shapes with different optical systems. The percentage of direct (downward) component of these direct/indirect luminaires ranges from 0% to approximately 60% but is usually less than 20%. This reduction in direct downward component reduces glare. The smaller profiles of the T5 lamps and their ballasts versus T8 and T12 lamp systems lead to smaller luminaires with improved optical control. Luminaire designers take advantage of these features and design aesthetically pleasing compact luminaires for high-end luminaire design. These designs include combining computer-designed optical systems such as patented prism panels to induce light softly from the lamps and hemi-cylindrical acrylic diffusers to soften the high luminances of T5 high output (T5 HO) lamps. These direct/indirect T5 luminaires become a viable option for commercial lighting applications where smaller, visually appealing luminaires are in demand. The metric lengths may allow for a better fit into 2x2 and 2x4 ceiling grids.

Luminaire manufacturers often use the same luminaire housings for T5 lamps as T8 (and sometimes T12) systems. Because the lengths, socket sizes, and ballasts of T5 lamps differ from those of T8 or T12 systems, the luminaire housings have two kinds of mountings for sockets: one for miniature bi-pin sockets of T5 lamps and the other for medium bi-pin sockets of T8 and T12 lamps and flexibility of mounting ballasts with different dimensions. In this case, designers use an optimal reflector for each lamp type.

Figure 17-1. Direct/Indirect Pendant Luminaire

Direct/indirect pendant luminaire

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