Photometry for T5 high-output lamps and luminaires

The newly developed T5 lamps continue to become increasingly popular as ballast and luminaire manufacturers develop smaller and more energy efficient products. However, unlike the T8 and T12 lamps, the linear T5 and T5HO lamps are designed with an optimal operating temperature of 35 degrees Celsius instead of the commonly adopted temperature of 25 degrees Celsius. Concerns arise regarding operating temperature selection and the unexpected results from the photometry of the luminaires employing these lamps. In this paper, we address the issue of the luminous flux of the T5HO lamps at two important operating temperatures: 25 and 35 degrees Celsius. Our finding is that if the T5HO lamp is stabilized horizontally, the resulting difference in the luminous flux of the lamp between the two temperatures is an average of five percent. We also propose a photometric testing method for T5HO-lamp luminaires that will produce the accurate photometry. This proposal calls for bare-lamp measurements to be performed at the lamp operating temperature inside the luminaire housing. Finally, we devise an abbreviated alternative for the proposed method that is simple and practical for most of the T5HO-lamp applications.