LED Lighting: What You Need to Know Before You Buy

This article is taken from Source: http://www.sxc.hu/ , good tips and information regarding the LED lighting.
Key Points

• Only one-third of LED lighting products tested live up to manufacturer's claims.
  
• Look for product testing, accreditations, warranty, chip suppliers, and other indications of quality.
  
• Consider product features such as light output and lumen depreciation for your specific application.

Light-emitting diode (LED) technology is one of the most exciting developments in energy-efficient lighting. Like any new technology however, it has experienced growing pains. In fact, only about one-third of all LED lighting products tested live up to manufacturer's claims, according to U.S. Department of Energy research (DOE 2009). Given these odds, how can you be sure you have the information you need to make the right purchasing decision?
A panel of lighting experts at the 2010 LightFair International Conference addressed this question and developed a checklist of things to look for. The following is a list of the 10 questions you should ask when choosing LED products for your lighting application:

1. To what quality standards has the product been tested? Quality standards for LED products are still in the early stages of development, but testing procedures are available from the following trusted organizations:
   • UL 8750 Safety Standard for LED Equipment for Use in Lighting Products is available through Underwriter's Laboratory.
     
   • The Illuminating Engineering Society of North America has developed IESNA LM-79-08 Approved Method: Electrical and Photometric Measurements of Solid-State Lighting Products and IESNA LM-80-08: Approved Method: Testing Lumen Maintenance of LED Light Sources to measure overall performance and light output over time.
2. What quality accreditations apply?
   
   • ENERGY STAR qualified LED lighting products must meet specific criteria in brightness, lumen maintenance, color quality, and other performance standards.
   • Lighting Facts Label. A voluntary program sponsored by the U.S. Department of Energy (DOE), the label displays important measures such as light output, efficacy, color rendering, and light color—tested according to IESNA LM-79-08 standards
   • Next Generation Luminaires is an annual design competition highlighting LED products that demonstrate high-quality lighting and consistency, glare control, lumen maintenance, and luminaire appearance.
3. Whose LED chips are used in the luminaire? Chips from recognized suppliers such as Nichia, Cree, Showa Denko, Philips, Epistar, and OSRAM, are an indication of quality in LED products.
   
4. What color characteristics are specified? Color rendering index (CRI) is a measure of a light source's ability to reproduce light compared to a natural light source. Color correlated temperature describes the relative appearance of a light source (whether it appears more yellow or blue). IESNA LM-79-08 includes testing methods for both, and ENERGY STAR qualified LED products must meet minimum color-quality measurements.
   
5. What efficacy is specified? Efficacy is the ratio of light output (in lumens) to power input—measured in watts. ENERGY STAR qualified LED products must meet minimum efficacy requirements. Lighting Facts Label participants are required to test for efficacy.
   
6. What is included in the product warranty? Things to look for include, maximum number of diode failures, acceptable color change, power supply requirements, dimmer use/type, and maximum LEDs per circuit, which may or may not be specified in the warranty. The length of warranty is evidence of a manufacturer's confidence in product life.
   
7. What is the acceptable lumen output and depreciation? Lumen output depreciates over time, and according to the DOE, research has shown that occupants will accept gradual light reductions of up to 30% with little notice. Therefore, 70% of the initial light level may be a good threshold for useful life in general lighting applications. In achieving acceptable illumination for your application, also consider the directional nature of LED luminaires and outdoor light quality improvements. Compare the lumen output of the LED product with that of the lighting that is being retrofitted. The Lighting Facts label ensures that LED products meet your performance expectations.
   
8. What Light Loss Factor (LLF) should be applied? LLF refers to operating or environmental factors that interfere with light transmission. Be sure to take into account optical losses, ambient temperature, diode failures, lumen depreciation and dirt depreciation.
   
9. What dimming characteristics are required? Consider LED performance at dimming levels as well as dimming range and dimming method.
   
10. What impact will LED in-rush have on your lighting system? LED current in-rush may occur as frequently as every one-half cycle. This may affect how many LEDs can be ganged together on one dimming control, for instance.

Getting the answers to these questions will help you make a more informed purchasing decision and find the right product to fit your needs.

 

References

Dakin, Jimmalee; Lund, Eric; Ziegenbein, Paula; Zinkon, Ardra. LEDs: The Magical Mystery Tour and the map to guide you through. 2010 LightFair International Conference. Las Vegas, NV
U.S. Department of Energy (DOE). CALiPER Summary Report. DOE Solid State Lighting CALiPER Program, October 2009.