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LD+A The Magazine of the Illuminating Engineering Society of North America

LED Testing & Application  


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Whether the space is an office, retail or museum, there’s much to consider before specifying LED luminaires for an interior application. Christopher Ruud, president of Ruud Lighting, Inc—a Cree Company, narrows the list to five key issues.

  1. Sustained Illumination Performance. After establishing the required maintained illumination performance requirements for an application and the application timeframe, collecting credible product performance data--such as photometric data derived from LM-79-08 photometric testing and specific lumen maintenance values derived from testing correlated to LM-80-08 testing combined with TM-21 methods--is critical.

    Don’t fall into the trap of using the same lumen maintenance factor for all manufacturers’ products across the board. Unlike technologies of the past, manufacturers now have the ability to impact lumen maintenance based on product design for the various electrical and environmental operating conditions to which the luminaires are subjected. Results can and do vary. Using a universal lumen maintenance value for all products can actually penalize the good products and makes it more likely that an inferior product will be selected. Upon fairly evaluating products at the illumination performance level, luminaires that fail to meet the required maintained illumination performance requirements must be disqualified from consideration so that more time can be spent on evaluating the acceptable candidates.
  2. Sustained Economic Performance. The first cost of the product is only one factor to consider. Managing future risk, through warranties, is also important. While having a strong warranty from a reputable company is good, being able to combine this with a high degree of certainty that the warranty terms and conditions will never need to be exercised is even better. How is this accomplished? Look to credible data, as previously mentioned, that help predict reliability and performance. Credible performance data regarding the reliability of the power supply (driver) or color quality and long-term color stability are just a few ways to gain insight on expected performance over time and can help ensure that expected performance will match real world results.
  3. Color Quality Specifications and Metrics. Most of us are familiar with Correlated Color Temperature (CCT) and Color Rendering Indices (CRI), both vital to proper lighting schemes and applications. But as LED products continue to become more prevalent in indoor spaces, so will discussions focused on expanded CRI, including R9 values, color consistency and stability characterized with Duv and MacAdam Ellipse values. These more sophisticated metrics will lead to more discriminating color quality specifications.
  4. Optimizing Installation and Power Flexibility. LED products offer the opportunity for alternative methods of installing and powering compared to more traditional sources and technologies. LED luminaires utilizing Power Over Ethernet (POE) is one example. POE allows power and data to be provided over the same service line. This can allow for greater simplicity in LED product design and installation. In addition, such systems may have significantly lower installation and related material costs compared to more traditional fixture installations. Therefore, when evaluating such luminaires it will be critical to consider total installed costs versus simply the cost of the luminaire itself. In addition, systems utilizing POE can also provide increased flexibility that can allow luminaires to be easily added or moved, as well as provide the ability to add controls-related functionality.
  5. Dimming Capabilities. LED solutions become even more efficacious (more lumens per watt) when dimmed, and the rate of lumen depreciation on LED luminaires is also reduced through dimming. And while many LED luminaire manufacturers offer dimming functionality as a standard product feature, it is important to understand your specific dimming needs. Controls compatibility requirements and range of dimming needed are just a couple of critical factors that must be considered. This is especially true when trying to integrate LED luminaires with an existing dimming system.



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