Key Recommendations from NGLIA LED Lifetime Report

The Next Generation Lighting Industry Alliance (NGLIA) has recently released the third edition of  “LED Luminaire Lifetime: Recommendations for Testing and Reporting”. The alliance membership includes some lighting industry heavy weights including Philips, Cree and GE lighting. Below are some of the key recommendations from the report:

Recommendations from the Second Edition: 

The following is a summary of the recommendations from the second edition of LED Luminaire Lifetime:

    Lumen depreciation is not a proxy for luminaire lifetime. 

       Unchanged: This remains an important point. The LED package may not be dominant in determining product lifetime.

    Consider only light output in defining lifetime. 

       Modified: This recommendation now includes color shift for those applications where it is relevant.

    Use overstress testing to identify design flaws and manufacturing defects.

       Unchanged: The concept of “robustness” testing, while not a full reliability test, can provide useful screening of products.

    Indicate if a product is serviceable or not. 

Unchanged: Additional discussion of what serviceability means in terms of reliability is in Section 2.2.1.4

    LM-803 data with TM-214 can predict lumen depreciation but not lifetime.

       Unchanged: This relates to the idea that package lumen depreciation is not the only possible failure. 

    Develop standard ways to characterize drivers for SSL use.

       Unchanged: While driver characterization is better than it was, there is still a need for testing standards.

    End of life as defined in this document excludes color shift.

       Modified: For products designed for applications requiring color stability, this is not the case.

    To deal with color shift, designate products in one of three categories (lamp replacement, standard grade, specification grade).

        Modified: Designate as color-stable, if relevant, and redefine categories. 

    Develop standard qualitative descriptions of the degree of color shift.

       Unchanged: Discussed in this document.

    Define standard luminaire lifetime. 

       Dropped: There is no consensus around this approach at this time.

    Reported lifetime should have at least a 50% confidence level. 

       Unchanged: This recommendation has not been widely observed but should be.

    Use LM-795 for full luminaire characterization. 

       Unchanged.

    Develop and document a change control process. 

       Unchanged: This is good business practice for manufacturers, but not intended to suggest any industry

standard.

    Develop a capability for statistical system design for reliability. 

       Dropped: Because of the variety of designs and applications, this is not realistic as a general industry

objective, although proprietary methods for specific product groups can be helpful to manufacturers.

    Add standard LED luminaire lifetime to the LED Lighting Facts® label.6 

       Dropped: While this may have been useful when there were a relatively few types of products available, with the proliferation of products and applications, there is now too much variation in the lifetime for a general recommendation.  

Recommendations for Manufacturers: 

    Provide clear product warranties, report compliance with industry standard measurements, and communicate your use of and commitment to best practices for designing and developing long-life, reliable products.

 IES LM-80-08, Approved Method: Measuring Lumen Depreciation of LED Light Sources, http://www.ies.org/store/product/approved-

method-measuring-lumen-maintenance-of-led-light-sources-1096.cfm. 

 IES TM-21-11, Projecting Long Term Lumen Maintenance of LED Light Sources, http://www.ies.org/store/product/projecting-long-term-

lumen-maintenance-of-led-light-sources-1253.cfm. 

 IES LM-79-08, Approved Method: Electrical and Photometric Measurements of Solid-State Lighting Products,

http://www.ies.org/store/product/approved-method-electrical-and-photometric-measurements-of-solidstate-lighting-products-

1095.cfm. 

 LED Lighting Facts, http://www.lightingfacts.com/.  

    Develop, implement, and adhere to design and engineering recommended best practices and document them in a form suitable for general lighting users.

    Achieve industry consensus on screening tests which can identify product designs that are unlikely to meet vendor claims of reliability and lifetime (may be for specific product groups and may involve specific performance ranges). 

    Continue to improve and develop industry-consensus methods for measuring and reporting key LED product attributes, such as lumen and color maintenance, particularly efforts to accelerate such testing.

Recommendations for Buyers:

    Focus on qualifying suppliers. Understand what methods the vendor is using to support reliability or lifetime claims, and require data. As they become available, require compliance with industry-consensus robustness tests.

    Understand the warranty. What is covered and what is not? Is the warranty period a reasonable fraction of the claimed lifetime? Will the manufacturer have compatible replacement parts as applicable, when needed?  

    Avoid using products for which reliability claims are based on unreliable proxies for luminaire lifetime, such as the lumen maintenance of the LED package. Require and examine additional luminaire product or subsystem data from your qualified manufacturer to support any such claim.  

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