Shedding light on LED purchasing

4 April 2013
It is predicted that 80 per cent of the lighting market will be LED by 2020. Energy managers and maintenance teams will no doubt be excited about a future of reduced energy consumption and lean maintenance regimes. However, will lighting’s ‘holy grail’ deliver all the expected benefits? LED technology, unlike the incandescent light bulb, was not invented as a commercial light source - early applications were indicator and traffic lights. As LED technology evolved, the significant increase in lumen output enabled lighting manufacturers to use LED as a light source. The development of LED, within the lighting sector, challenges traditional procurement processes. Commercial light sources, such as fluorescent, halogen and ceramic metal halide, operate within known criteria and standards. In addition, manufacturers lighting products are comparable. LED does not follow traditional lighting technology characteristics or rules. There are eight key issues to consider when specifying and purchasing LED luminaires and lamps.
  • Intellectual property. Does the LED have the required intellectual property licence?
  • Thermal management. Are junction temperatures within operating tolerances?
  • Driver. Remote or integral, does the driver have an equal or superior life rating when compared to the LED?
  • Life. Is life defined in accordance with LM70 and LM80 tests?
  • Colour rendition. Is the colour shift percentage defined?
  • Lumens. How is lumens output measured?
  • Wattage. Is the published wattage LED or system?
  • Warranty. How is failure defined?
While LED is cool to the touch, heat is generated during operation. The efficient removal of heat, away from the LED, determines life. There is a direct relationship between operating power – heat generated – lumen output – life. As power is increased, the lumen level increases together with heat generation. If the generated heat is not controlled, LED life is reduced. What does this mean for purchasing? First, the age old rule of ‘if it sounds too good to be true it probably is’ should be applied. Even some major lighting brands have been found wanting with their performance and quality claims. There are no standards: for example, a recent review of six LED 1500mm tubes revealed performance between 16 watts – 24 watts, 1,200 – 1,700 lumen, 30,000 – 50,000 hours. Without constants, how can LED be purchased? Then there is the price. While LED does deliver energy and maintenance efficiency, often with excellent return on investment, the initial outlay can exceed the budgets of many businesses. For example, 50 halogen GU10 bulbs will cost £100; the LED GU10 equivalent will cost £650. Those involved in purchasing LED should develop mutually beneficial business relationships with independent LED specialists and prepare robust specifications. The LED specification, as a minimum, should cover the eight key points previously detailed. ☛ Dave Tilley is a lighting consultant at NRGstar
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