Thanks to the variety of systems manufacturers offer, managers will have to narrow the field of products to test. One problem managers face, particularly when reviewing a manufacturer’s published data, is knowing they are comparing apples to apples. This issue is particularly difficult, given the rapid development of LED light sources. Not all manufacturers might use the same system to rate the performance of their fixtures.
The Illuminating Engineering Society of North America (IES) has developed standards that can help. One standard is L70. All luminaries suffer from a decrease in light output as lamps age. L70 identifies in hours the time it takes for the light level of a particular solid-state source to decrease to 70 percent of its original light level.
The 70 percent value was selected as this is the level at which the human eye begins to notice the decrease. For a LED light source with a rating of 50,000 hours, 50 percent of the light sources will be producing light at 70 percent of their original output.
When the field test is completed, managers need to carefully review the results and compare the different costs for the systems that are acceptable. In some cases, a fairly obvious choice will emerge that offers above-average energy savings and below-average maintenance requirements and is widely accepted by the users of the space.
In other cases, managers must accept a system that most closely meets lighting upgrade’s range of goals. The final selection will depend on those factors, as well as on the first costs.
James Piper, P.E., is a national facilities consultant based in Bowie, Md. He has more than 25 years of experience with facilities maintenance and management issues.
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