Lumen maintenance

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In LED lighting, lumen maintenance is the luminous flux remaining (expressed as a percentage of the initial output) at any selected elapsed operating time. Lumen depreciation is the luminous flux lost over time, and thus the complement of lumen maintenance.[1]

Lumen maintenance compares the amount of light produced from a light source or from a luminaire when it is brand new to the amount of light output at a specific time in the future. For instance, if a luminaire produced 1,000 lumens of light when it was brand new and now produces 700 lumens of light after 30,000 hours, then it would have lumen maintenance of 70% at 30,000 hours.[2] Useful lifetime estimates for LED lighting products are typically given in terms of the expected operating hours until light output has diminished to 70% of initial levels (denoted L70 life).[3]

There are a number of methods for controlling lumen maintenance areas:

  • Installing photoreceptors tied directly to ballasts, controlling the voltage output to the lamps based on the set level of luminance.
  • Connecting dimming ballasts directly to an energy management system that has been programmed for the expected depreciation of the lamps; the energy management system directs the output of ballasts as necessary to maintain required lighting levels over time.
  • Manually verifying lighting levels in a space by using photometers in specific locations, and then manually setting the system to meet lighting requirements.[4]

IES LM-80[edit]

IES LM-80 is the Department of Energy (DOE) approved testing method for measuring lumen depreciation of solid-state (LED) light sources, arrays and modules.[5] The Illumination Engineering Society (IES) and the Department of Energy Solid State Lighting Standards Development group worked together to create the LM-80 test criteria.

References[edit]

  1. ^ "Cree Xlamp Long-Term Lumen Maintenance" (PDF). Cree.com. Cree Inc. Retrieved 24 July 2013. 
  2. ^ "LED Reliability and Lumen Maintenance". Retrieved 24 July 2013. 
  3. ^ "Guide to Evaluating LED Lumen Maintenance" (PDF). Retrieved 24 July 2013. 
  4. ^ "Lumen maintenance". ATeam.LBL.gov. Retrieved 28 May 2015. 
  5. ^ "Understanding IES LM-79 & IES LM-80" (PDF). Retrieved 18 July 2015.