T5 Lamps and Ballasts

T5 Lamps and Ballasts

Cove lighting systems can benefit from T5 lamps and their new ballasts. These 5/8-in. diameter lamps are 12-18% more efficacious than T8 lamps, but they are not intended to replace T8 technology. T5 systems are especially suitable for the higher temperatures found in indirect, confined cove systems (where there is little or no air circulation), because they are designed to produce their peak light output at 35 degrees C (95 degrees F) vs. 25 degrees C (77 degrees F) for T12 and T8 lamps.

New ballast models can power one or two standard T5 lamps of any wattage (14, 21, 28, or 35 W), since all lamps in the standard T5 family operate at the same current (170 milliamps). All models have the same surface brightness, so no matter what length lamp is used to fill out the length of the cove (549, 849, 1149, or 1449 millimeters), cove brightness is uniform.

To increase brightness in coves and for other indirect lighting applications, T5HO lamps are recommended. T5HO lamps have the same physical measurements as the lower wattage, standard T5 lamps, but provide higher light output. T5HO lamps generate up to twice the light output of standard T5 lamps and nearly twice the light output of T8 or T12 systems, which allows half the number of lamps to be used.

The surface brightness of T5HO varies with various power ratings (24, 39, 54, and 80 W). The lamps operate on different currents, so each lamp wattage requires a unique ballast. At 83 to 94 lm/W per watt, they are about 10-15% less efficacious than standard T5 lamps and up to 8% less efficacious than T8 systems.

Both standard T5 and T5HO lamps maintain superior light output over time, only losing 5% of their initial lumen rating in the first 40% of rated life. Both lamp types have excellent color rendering index (CRI) ratings greater than 80.

A new, versatile T5HO ballast, designed to operate two, three, or four F54 (~45-in) lamps has been announced. Multi-lamp versatility, remote mounting, and a high-low switching option make this model attractive for many new applications. Dimming ballasts are also available for T5HO lamps.