The Illuminating Engineering Society of North America (IES) has announced a new document, Projecting Long Term Lumen Maintenance of LED Light Sources (TM-21-11). The document recommends a method for projecting the lumen maintenance of LED light sources from the data obtained by the procedures found in IES document Approved Method for Measuring Lumen Maintenance of LED Light Sources (LM-80-08).
LED light sources provide a very long usable life but light output gradually depreciates over time. TM-21-11 provides the method for determining when the “useful lifetime” of an LED is reached, which can vary from manufacturer to manufacturer and between different LED package types produced by a single manufacturer.
It is important to note that TM21 covers only LED light source components—package, modules and arrays—not entire light fixtures. As a complete fixture features other components that can affect service life (i.e., driver, optics, thermal management, housing), any of these other components can cause the fixture to fail even if the LEDs are still healthy.
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