> Quick answer: Reputable manufacturers use the IES LM-80-08 and TM-21-11 framework to test LED lumen maintenance before shipment, ensuring long-term performance through standardized, third-party recognized methods [1][4][15].
LED lamps have become a popular choice for solar lighting in Romania due to their energy efficiency and durability. But how do manufacturers ensure that these lights will maintain their brightness over time? The answer lies in rigorous testing protocols designed by the Illuminating Engineering Society of North America (IES) [1][4].
Standardized Testing Methods: LM-80-08 and TM-21-11
Reputable manufacturers rely on standardized, third-party recognized methods developed by IES to test LED lumen maintenance before shipment. The foundation of these tests is the LM-80-08 method [2][15]. This process involves measuring lumen depreciation over a minimum of 6,000 hours under controlled conditions [2][15].
LM-80-08: Measuring Lumen Depreciation
During an LM-80 test, LED samples are placed in temperature-controlled thermal chambers and operated at multiple case temperatures—typically three—to simulate different thermal environments. Data on luminous flux, chromaticity, color temperature (CCT), and color rendering (CRI) is collected at regular intervals, often every 1,000 hours [15][19], with failures recorded [13]. This data provides the necessary raw information for long-term performance projections.
TM-21-11: Extrapolating Long-Term Performance
The second critical step is applying TM-21-11, which provides a standardized statistical method to extrapolate LM-80 data and predict long-term lumen maintenance [1][9]. This method enables manufacturers to estimate performance over the claimed product life—often 25,000 to 50,000 hours [17]. For instance, for the Energy Star label, an LED luminaire must demonstrate specific lumen maintenance levels after at least 6,000 hours of operation [4].
In-Situ Testing: Beyond LM-80
While LM-80 focuses on individual LED sources, real-world performance depends on the entire lighting system. Manufacturers often conduct in-situ testing to evaluate the LED system as installed in its intended fixture [7]. This is crucial because operating temperatures can vary significantly from controlled conditions and have a significant impact on lumen maintenance.
IES TPC Recommendations
The IES recommends including operational duty cycles with on/off cycling to better reflect real-life conditions. However, exact duty cycle durations or ratios are not specified in the sources [23].
Challenges and Limitations
Despite the robustness of LM-80 and TM-21-11, there are limitations. For instance, LM-80 does not account for degradation in components like plastic optics or drivers, prompting the development of new standards such as LM-84 and TM-28 [9][17]. Additionally, 6,000-hour test durations may be insufficient for products rated for over 30,000 hours [15].
Third-Party Verification and Certification
Independent third-party verification is increasingly valued. Programs like DOE’s GATEWAY demonstrate real-world performance in field applications, complementing laboratory results [19]. These evaluations are crucial for validating performance, especially in complex environments such as museums [8].
Comparison of Testing Methods
| Method | Description |
|––––––|––––––––––––––––––––––––––––––––-|
| LM-80-08 | Measures lumen depreciation under controlled conditions over 6,000 hours. |
| TM-21-11 | Extrapolates long-term performance based on LM-80 data using statistical methods. |
| In-situ Testing | Evaluates the LED system as installed in its intended fixture to simulate real-world conditions. |
Key Takeaways
- Reputable manufacturers use standardized IES methods like LM-80 and TM-21 for testing lumen maintenance.
- Third-party data from suppliers and extrapolation are critical for meeting certification standards.
- In-situ testing is essential but lacks specific operational duty cycle recommendations.
Frequently Asked Questions
[
{
„q”: „What is the purpose of LM-80 testing?”,
„a”: „LM-80 testing measures lumen depreciation under controlled conditions over a minimum of 6,000 hours to ensure long-term LED performance [2][15].”
},
{
„q”: „How does TM-21 help in predicting LED life?”,
„a”: „TM-21 provides a standardized method for extrapolating LM-80 data to predict lumen maintenance over the claimed product life, often up to 50,000 hours [1][9].”
},
{
„q”: „Why is in-situ testing important?”,
„a”: „In-situ testing evaluates LED systems under real-world conditions, accounting for variations in operating temperature and other environmental factors [4][7].”
}
]
References
- [1] Lumen-maintenance_testing_for_LED_lamps_light_engines_Buildings__ea530613 — authority
source passage
# Lumen-maintenance testing for LED lamps, light engines and luminaires (MAGAZINE) Source: Blog/Web URL: https://www.buildings.com/architecture/interiors/article/55255355/lumen-maintenance-testing-for-led-lamps-light-engines-and-luminaires-magazine Author: Date: 2012-02-02 +++++ This article was published in the February 2012 issue of LEDs Magazine. View the Table of Contents and download the PDF file of the complete February 2012 issue. +++++ It is widely understood that measuring lumen maintenance is critically important for determining the life of LED lighting products. In the past few years, the Illuminating Engineering Society of North America (IESNA) has developed two test methods that address the lumen maintenance of LED light sources used in such products. LM-80 is an approved method for measuring lumen depreciation of LED light sources, and TM-21 is a technical memorandum which specifies how to extrapolate the LM-80 data in order to make long-term lumen-maintenance projections. Beyond the LED, other components at the LED lighting-system level also can impact the long-term lumen maintenance. These components include, but are not limited to, LED lamps, engines, luminaires, drivers, thermal-management devices and optical components. Over time, these components may experience some change or degradation. In particular, the plastic elements used in the optics may change in several ways, including light transmittance, haze and undesired color change. In turn, the overall li
- [2] Labeling_and_Certification_Testing_Issues_by_UL_LED_professional__c8c27684 — authority
source passage
is necessary and what affects the workflow of the certification process. His main aim is to clarify the time it takes to test LED lighting products for the applicable industry performance standards and to qualify products for the EPA Energy Star program. There are two approved methods for LED light sources that result in replicable test measurements and a reliable comparison of test data that is generated by different laboratories. IES LM-80-08 “Measuring Lumen Maintenance of LED Light Sources” contains a process whereby changes in light output are measured under controlled conditions. This testing is typically conducted by the manufacturer of the individual LED light source. That data is then supplied to an end-user so that it may be utilized in future qualification testing. IES LM-79-08 “Electrical and Photometric Measurements of Solid-State Lighting Products” describes the test methods for measuring Solid-State lighting luminaires or lamps. These test methods incorporate the use of absolute photometry for testing these products rather than relative photometry which had been the industry standard. Figure 3: Typical lumen maintenance temperature parameter measuring points for LM-80 test Test durations for each of these standards vary and can be summarized as the following: • For LM-80 testing, the units under test (UUT) will be driven for a period of at least 6,000 hours (250 days) under specified ambient conditions. Photometric and Chromaticity data is collected initially a
- [4] Labeling_and_Certification_Testing_Issues_by_UL_LED_professional__c8c27684 — authority
source passage
are two options for determining lumen maintenance: – Option 1: This option requires In-Situ testing along with the LM-80 data supplied from the individual LED provider. In-Situ testing takes approximately 1 day to complete. – Option 2: For luminaire manufacturers who do not have LM-80 data, the fixture would be tested for 6,000 hours. This option is rarely utilized as most individual LED manufacturers supply the LM-80 data. – For additional information on Options 1 or 2, please refer to Energy Star® Program Requirements, Product Specification for Luminaires (Light Fixtures), V1.2. LM-80 Test The LM-80 test report is essential to obtain the Energy Star label. The LM-80 test reports must illustrate that subcomponent lumen maintenance testing was conducted in accordance with the testing method outlined in IES LM-80-08, except as otherwise detailed in this document or in Energy Star specifications. An LED Luminaire PASSES the Lumen Depreciation requirements if: • The LM-80 test report for the package, array or module demonstrates lumen maintenance of: – ≥91.8% (indoor residential) – ≥94.1% (outdoor residential and all commercial) • Measured during the in-situ temperature measurement test (UL1598/153), at the hottest TMP evaluated at ≥6,000 hours • The drive current measured in the fixture is less than or equal to the drive current specified in the LM-80 test report LM-79 Test LM-79 testing applies to LED products that incorporate control electronics and heat sinks. This covers co
- [7] Lumen-maintenance_testing_for_LED_lamps_light_engines_Buildings__ea530613 — authority
source passage
auxiliary equipment and fixtures. These conditions are not accounted for in the LM-80 testing of LED sources. As a result, it may become necessary for the IES to provide recommendations on these test conditions, and test methods would need to be designed to give comparable results when adopted by various testing laboratories. A lumen-maintenance test standard for LED lamps, engines and luminaires is still being developed, with multiple drafts created, and some preliminary balloting already completed. Different from the LM-80 test standard, this new document will address the tests that are more uniquely applicable to LED lighting systems, including temperature conditions, operational duty cycle and test duration. For LED sources, LM-80 recommends three case temperatures at which testing is performed. Often, the LEDs being tested are placed in temperature-controlled thermal chambers with sophisticated active-cooling systems. These precisely set the LED case temperatures to meet test requirements, with each test running for a minimum of 6000 hours at each case temperature. It can be cost-prohibitive and impractical to test entire LED light systems – such as large luminaires for outdoor roadway lighting fixtures or chandeliers for indoor lighting – in the temperature-controlled chamber for long periods of time. Instead, the TPC recommends LED lighting systems be tested in a condition as close as possible to the installation orientation and mounting method, which in many cases is
- [8] LED_Lighting_in_Museums_and_Art_Galleries_Technical_-_Canadaca__7f9b6307 — authority
source passage
Obtain LM-79 reports (lamp characteristics) from lamp manufacturers. – Check the DOE CALiPER website for impartial test data. – Check the EnergyStar Light Bulbs website and the LED Lighting Facts database (consult endnote 1) for characteristics of products currently available on the market. – Consult Technical details for larger projects. Purchase trial lamps – Once you have made preliminary decisions on several candidate lamps, purchase a few and evaluate them in situ, preferably with colleagues. Check the appearance of the lamp from the side for glare. Check the appearance of the light on blank walls. Check the appearance of the objects illuminated by the lamp. Check the appearance of your skin under the lamp (we are especially attuned to how our skin should look under good-quality light). – If you purchased dimmers, test them with the lamps. Check for flicker across the whole range of intensities. – Test trial lamps, especially those you are considering for purchase, in the fixtures planned for use for as long as possible, and at least a week, to see if they change colour or overheat and fail. Before purchasing large numbers of lamps – Ask for products from companies you know or whom you trust or that have a documented support history. – Get a written warranty that encompasses light output, colour variation (Duv) over time as well as failure of chips and electronics, and which includes labour. A one-year warranty is common, but for longer periods of time the coverage may b
- [9] New_standards_will_enable_lumen_maintenance_projections_Buildings__373ebe28 — authority
source passage
# New standards will enable lumen maintenance projections for SSL (MAGAZINE) Source: Blog/Web URL: https://www.buildings.com/home/article/55259249/new-standards-will-enable-lumen-maintenance-projections-for-ssl-magazine Author: Date: 2013-04-30 In August 2011, the Illuminating Engineering Society (IES) published a document to provide the SSL industry with a recommendation for projecting long-term lumen maintenance for LEDs. The document, TM-21-11, reflects over three years of dedication and hard work by the experts on the IES Testing Procedures Committee (TPC). Though not perfect, TM-21- 11 gives users a consistent, reasonable, and reliable approach to make lumen maintenance projections for LEDs used in SSL products. This document is a useful tool for SSL product design, development, and qualification for manufacturers, specifiers, and qualifiers. Because components other than LEDs, such as optical elements, also contribute toward lumen decay over time in LED lamps and luminaires, an SSL final product-level lumen maintenance test is also necessary. To that end, the IES TPC started to develop a new document, LM-84, to describe lumen and color maintenance testing procedures. For SSL products — and some major components used in the products — common qualification and reliability tests used by manufacturers prior to a product being released are no longer sufficient for achieving a reasonable time to market. The longer lifetime of SSL products compared to other lighting products w
- [13] Understanding_the_difference_between_LED_rated_life_and_Buildings__730bf80c — authority
source passage
samples that failed to produce light, then B50L70 (in hours) is obtained. Obviously, as is the case with lumen maintenance, it is not practical to conduct real-life tests to get B50L70 values when such a value can be as long as 30,000 hours, or nearly three and a half years. The challenge is how to make a projection using the data obtained in a shorter testing period. Projections LED manufacturers have been conducting studies and establishing practices for reliable approaches to project the rated life for LEDs; in general, there are two approaches. The first approach is to conduct LM-80 testing with a large sample size. The test data are collected for both light-output changes and failures. The data is then fitted into a mathematical model with a statistical-certainty band. In addition to the lumen-maintenance projection curve, the associated sample distribution bandwidth is also plotted. By analyzing the curve and bandwidth, an estimated B50L70 life is projected. The second approach is to conduct the lumen-maintenance (LM-80) test separately from the accelerated-failure-modes test. Using TM-21, the lumen-maintenance projection can be established. The data collected in the accelerated-failure-modes test are modeled with a different mathematical expression. The rated life is then projected by mathematically combining both models. There are some discussions in standardization organizations regarding development of a document or recommendation to address LEDs’ rated life. To hel
- [15] Knowledge_Base__d64b9e2d — authority
source passage
environment. The gasket will not shrink over time giving year after year of reliable service. LED Testing Standards LM-80-08 LM-80-08 is the latest testing standard for LED diodes and applies to the LED sources in a standard test environment, independent of a specific lighting fixture. Testing is performed for a minimum of 6,000 hours with data collection every 1,000 hours. During testing, LEDs are assessed for failure, chromaticity, luminous flux, color temperature (CCT) and color rendering (CRI). LM-80-08 allows the creation, by LED manufacturers, of predicted life charts to establish expected design life. It is not a direct measure of LED system performance, but it will provide the lighting professional with assurance that the LEDs used in our products have been tested for chromaticity stability and predicted lumen maintenance. We only use chips that have been tested to this standard. TM-21-11 TM-21-11is an industry accepted statistical method that utilizes LM-80-08 data combined with specific fixture measurements to project long-term lumen maintenance of LED light sources. LEDs, by their nature, will last a very long time when utilized in a properly designed environment, but this performance is dependent on the design parameters of the actual fixture. Drive current, in-situ temperature and other environmental factors can dramatically affect useful LED life. TM-21-11 gives the lighting professional a basis to judge long-term lumen maintenance life expectancy of a specific
- [17] New_standards_will_enable_lumen_maintenance_projections_Buildings__373ebe28 — authority
source passage
luminaires, and possibly other components as well. These lumen maintenance- related tests are in addition to the commonly practiced qualification tests used by manufacturers. Typically when measureable characteristics, such as luminous flux or color, are determined, these maintenance tests are running in normal operational and environmental conditions, but for much longer than qualification or stress test time periods. This is based on the idea that LED and SSL product performance decay behavior can only be authentically tracked with such tests if the acceleration factors are not standardized. There are no pass/fail criteria for these maintenance tests. Their goal is to record product decay results or operation failure of the product during the test. The more important and more practical need is to correctly interpret the test results so that both SSL makers and users will know the product performance status after long-term use, e.g., 30,000 – 50,000 hrs. TM-21-11 has addressed the issue for LEDs. With LM-84 almost complete, the industry also needs a consistent, reasonable, and reliable approach to use the LM-84 test results to make projections. Thus, IES TPC is developing a new document, TM-28, to meet this need. The basic principles of TM-28 should be the same as in TM-21-11: • The projection must be based on average test data, discounting the tested units that stop working during the test. • The mathematical basis used in TM-28 should not deviate from TM-21-11. • The proje
- [19] LED_Lighting_in_Museums_and_Art_Galleries_Technical_-_Canadaca__7f9b6307 — authority
source passage
at 6000 hours, with 10,000 hours preferred, and repeated testing was determined to be needed every 1000 hours. Since the LM-80 only documents lumen maintenance for the period of time it is conducted, a separate estimate method for lifetime (TM-21) is in development. These reports should be available on the manufacturer’s website or upon request. GATEWAY demonstrations This program supports demonstration projects of high-performance SSL products. The purpose is to capture empirical data and experience with in-the-field applications that save energy, are cost effective and maintain or improve light levels. These provide a source of independent, third-party data for use in decision making by users and lighting designers. The GATEWAY Program staff suggests that this data be considered in combination with other information relevant to the particular site and application under examination (DOE 2010). To date, the GATEWAY Program has documented one museum application, at the Field Museum, Chicago, Illinois, in November 2010. Other museums are being considered, including several art museums. Since all GATEWAY Program museum reports can be downloaded online, this is a good place to start examining the issues you are likely to experience. Note that the evaluation questionnaire and the analysis of simple payback from the Field Museum have been adapted and included in the present Bulletin. Replacements for linear lighting (fluorescent lamps) Replacing fluorescent lamps with LED lamps rai
- [23] Lumen-maintenance_testing_for_LED_lamps_light_engines_Buildings__ea530613 — authority
source passage
throughout the test. In practice, however, LED lighting systems are cycled on and off in almost all applications for both indoor and outdoor lighting. As has been demonstrated in the past, cycling lamps on and off has an impact on lamp life for other lighting systems such as high-intensity-discharge (HID) and fluorescent lamps. Although cycling may not have as dramatic an impact on LEDs, the driver electronics can be affected. Therefore, the TPC recommends that the burning cycle during lumen-maintenance testing should not be conducted in a constant on condition. Instead, the TPC specifies an operational cycle with certain periods of on time and off time. This cycling condition is intended to have a closer relationship to real-life LED system applications. Test duration The duration of testing is another variable to consider, and the area where experts have struggled the most to establish a standard. It is clearly understood that lumen maintenance over time usually cannot be detected over a short testing period. LM-80 specifies a minimum of 6000 hours of testing. However, for LED systems, including lamps, engines and luminaires, prolonged testing creates a large burden for manufacturers and the lighting industry. Any recommended testing procedure from the IES must present practical values for the duration of testing. A testing period that is too short may not lead to conclusive characteristics being identified. On the contrary, as stated above, a testing period that is too lon
# Lumen-maintenance testing for LED lamps, light engines and luminaires (MAGAZINE) Source: Blog/Web URL: https://www.buildings.com/architecture/interiors/article/55255355/lumen-maintenance-testing-for-led-lamps-light-engines-and-luminaires-magazine Author: Date: 2012-02-02 +++++ This article was published in the February 2012 issue of LEDs Magazine. View the Table of Contents and download the PDF file of the complete February 2012 issue. +++++ It is widely understood that measuring lumen maintenance is critically important for determining the life of LED lighting products. In the past few years, the Illuminating Engineering Society of North America (IESNA) has developed two test methods that address the lumen maintenance of LED light sources used in such products. LM-80 is an approved method for measuring lumen depreciation of LED light sources, and TM-21 is a technical memorandum which specifies how to extrapolate the LM-80 data in order to make long-term lumen-maintenance projections. Beyond the LED, other components at the LED lighting-system level also can impact the long-term lumen maintenance. These components include, but are not limited to, LED lamps, engines, luminaires, drivers, thermal-management devices and optical components. Over time, these components may experience some change or degradation. In particular, the plastic elements used in the optics may change in several ways, including light transmittance, haze and undesired color change. In turn, the overall li
is necessary and what affects the workflow of the certification process. His main aim is to clarify the time it takes to test LED lighting products for the applicable industry performance standards and to qualify products for the EPA Energy Star program. There are two approved methods for LED light sources that result in replicable test measurements and a reliable comparison of test data that is generated by different laboratories. IES LM-80-08 “Measuring Lumen Maintenance of LED Light Sources” contains a process whereby changes in light output are measured under controlled conditions. This testing is typically conducted by the manufacturer of the individual LED light source. That data is then supplied to an end-user so that it may be utilized in future qualification testing. IES LM-79-08 “Electrical and Photometric Measurements of Solid-State Lighting Products” describes the test methods for measuring Solid-State lighting luminaires or lamps. These test methods incorporate the use of absolute photometry for testing these products rather than relative photometry which had been the industry standard. Figure 3: Typical lumen maintenance temperature parameter measuring points for LM-80 test Test durations for each of these standards vary and can be summarized as the following: • For LM-80 testing, the units under test (UUT) will be driven for a period of at least 6,000 hours (250 days) under specified ambient conditions. Photometric and Chromaticity data is collected initially a
are two options for determining lumen maintenance: – Option 1: This option requires In-Situ testing along with the LM-80 data supplied from the individual LED provider. In-Situ testing takes approximately 1 day to complete. – Option 2: For luminaire manufacturers who do not have LM-80 data, the fixture would be tested for 6,000 hours. This option is rarely utilized as most individual LED manufacturers supply the LM-80 data. – For additional information on Options 1 or 2, please refer to Energy Star® Program Requirements, Product Specification for Luminaires (Light Fixtures), V1.2. LM-80 Test The LM-80 test report is essential to obtain the Energy Star label. The LM-80 test reports must illustrate that subcomponent lumen maintenance testing was conducted in accordance with the testing method outlined in IES LM-80-08, except as otherwise detailed in this document or in Energy Star specifications. An LED Luminaire PASSES the Lumen Depreciation requirements if: • The LM-80 test report for the package, array or module demonstrates lumen maintenance of: – ≥91.8% (indoor residential) – ≥94.1% (outdoor residential and all commercial) • Measured during the in-situ temperature measurement test (UL1598/153), at the hottest TMP evaluated at ≥6,000 hours • The drive current measured in the fixture is less than or equal to the drive current specified in the LM-80 test report LM-79 Test LM-79 testing applies to LED products that incorporate control electronics and heat sinks. This covers co
auxiliary equipment and fixtures. These conditions are not accounted for in the LM-80 testing of LED sources. As a result, it may become necessary for the IES to provide recommendations on these test conditions, and test methods would need to be designed to give comparable results when adopted by various testing laboratories. A lumen-maintenance test standard for LED lamps, engines and luminaires is still being developed, with multiple drafts created, and some preliminary balloting already completed. Different from the LM-80 test standard, this new document will address the tests that are more uniquely applicable to LED lighting systems, including temperature conditions, operational duty cycle and test duration. For LED sources, LM-80 recommends three case temperatures at which testing is performed. Often, the LEDs being tested are placed in temperature-controlled thermal chambers with sophisticated active-cooling systems. These precisely set the LED case temperatures to meet test requirements, with each test running for a minimum of 6000 hours at each case temperature. It can be cost-prohibitive and impractical to test entire LED light systems – such as large luminaires for outdoor roadway lighting fixtures or chandeliers for indoor lighting – in the temperature-controlled chamber for long periods of time. Instead, the TPC recommends LED lighting systems be tested in a condition as close as possible to the installation orientation and mounting method, which in many cases is
Obtain LM-79 reports (lamp characteristics) from lamp manufacturers. – Check the DOE CALiPER website for impartial test data. – Check the EnergyStar Light Bulbs website and the LED Lighting Facts database (consult endnote 1) for characteristics of products currently available on the market. – Consult Technical details for larger projects. Purchase trial lamps – Once you have made preliminary decisions on several candidate lamps, purchase a few and evaluate them in situ, preferably with colleagues. Check the appearance of the lamp from the side for glare. Check the appearance of the light on blank walls. Check the appearance of the objects illuminated by the lamp. Check the appearance of your skin under the lamp (we are especially attuned to how our skin should look under good-quality light). – If you purchased dimmers, test them with the lamps. Check for flicker across the whole range of intensities. – Test trial lamps, especially those you are considering for purchase, in the fixtures planned for use for as long as possible, and at least a week, to see if they change colour or overheat and fail. Before purchasing large numbers of lamps – Ask for products from companies you know or whom you trust or that have a documented support history. – Get a written warranty that encompasses light output, colour variation (Duv) over time as well as failure of chips and electronics, and which includes labour. A one-year warranty is common, but for longer periods of time the coverage may b
# New standards will enable lumen maintenance projections for SSL (MAGAZINE) Source: Blog/Web URL: https://www.buildings.com/home/article/55259249/new-standards-will-enable-lumen-maintenance-projections-for-ssl-magazine Author: Date: 2013-04-30 In August 2011, the Illuminating Engineering Society (IES) published a document to provide the SSL industry with a recommendation for projecting long-term lumen maintenance for LEDs. The document, TM-21-11, reflects over three years of dedication and hard work by the experts on the IES Testing Procedures Committee (TPC). Though not perfect, TM-21- 11 gives users a consistent, reasonable, and reliable approach to make lumen maintenance projections for LEDs used in SSL products. This document is a useful tool for SSL product design, development, and qualification for manufacturers, specifiers, and qualifiers. Because components other than LEDs, such as optical elements, also contribute toward lumen decay over time in LED lamps and luminaires, an SSL final product-level lumen maintenance test is also necessary. To that end, the IES TPC started to develop a new document, LM-84, to describe lumen and color maintenance testing procedures. For SSL products — and some major components used in the products — common qualification and reliability tests used by manufacturers prior to a product being released are no longer sufficient for achieving a reasonable time to market. The longer lifetime of SSL products compared to other lighting products w
samples that failed to produce light, then B50L70 (in hours) is obtained. Obviously, as is the case with lumen maintenance, it is not practical to conduct real-life tests to get B50L70 values when such a value can be as long as 30,000 hours, or nearly three and a half years. The challenge is how to make a projection using the data obtained in a shorter testing period. Projections LED manufacturers have been conducting studies and establishing practices for reliable approaches to project the rated life for LEDs; in general, there are two approaches. The first approach is to conduct LM-80 testing with a large sample size. The test data are collected for both light-output changes and failures. The data is then fitted into a mathematical model with a statistical-certainty band. In addition to the lumen-maintenance projection curve, the associated sample distribution bandwidth is also plotted. By analyzing the curve and bandwidth, an estimated B50L70 life is projected. The second approach is to conduct the lumen-maintenance (LM-80) test separately from the accelerated-failure-modes test. Using TM-21, the lumen-maintenance projection can be established. The data collected in the accelerated-failure-modes test are modeled with a different mathematical expression. The rated life is then projected by mathematically combining both models. There are some discussions in standardization organizations regarding development of a document or recommendation to address LEDs’ rated life. To hel
environment. The gasket will not shrink over time giving year after year of reliable service. LED Testing Standards LM-80-08 LM-80-08 is the latest testing standard for LED diodes and applies to the LED sources in a standard test environment, independent of a specific lighting fixture. Testing is performed for a minimum of 6,000 hours with data collection every 1,000 hours. During testing, LEDs are assessed for failure, chromaticity, luminous flux, color temperature (CCT) and color rendering (CRI). LM-80-08 allows the creation, by LED manufacturers, of predicted life charts to establish expected design life. It is not a direct measure of LED system performance, but it will provide the lighting professional with assurance that the LEDs used in our products have been tested for chromaticity stability and predicted lumen maintenance. We only use chips that have been tested to this standard. TM-21-11 TM-21-11is an industry accepted statistical method that utilizes LM-80-08 data combined with specific fixture measurements to project long-term lumen maintenance of LED light sources. LEDs, by their nature, will last a very long time when utilized in a properly designed environment, but this performance is dependent on the design parameters of the actual fixture. Drive current, in-situ temperature and other environmental factors can dramatically affect useful LED life. TM-21-11 gives the lighting professional a basis to judge long-term lumen maintenance life expectancy of a specific
luminaires, and possibly other components as well. These lumen maintenance- related tests are in addition to the commonly practiced qualification tests used by manufacturers. Typically when measureable characteristics, such as luminous flux or color, are determined, these maintenance tests are running in normal operational and environmental conditions, but for much longer than qualification or stress test time periods. This is based on the idea that LED and SSL product performance decay behavior can only be authentically tracked with such tests if the acceleration factors are not standardized. There are no pass/fail criteria for these maintenance tests. Their goal is to record product decay results or operation failure of the product during the test. The more important and more practical need is to correctly interpret the test results so that both SSL makers and users will know the product performance status after long-term use, e.g., 30,000 – 50,000 hrs. TM-21-11 has addressed the issue for LEDs. With LM-84 almost complete, the industry also needs a consistent, reasonable, and reliable approach to use the LM-84 test results to make projections. Thus, IES TPC is developing a new document, TM-28, to meet this need. The basic principles of TM-28 should be the same as in TM-21-11: • The projection must be based on average test data, discounting the tested units that stop working during the test. • The mathematical basis used in TM-28 should not deviate from TM-21-11. • The proje
at 6000 hours, with 10,000 hours preferred, and repeated testing was determined to be needed every 1000 hours. Since the LM-80 only documents lumen maintenance for the period of time it is conducted, a separate estimate method for lifetime (TM-21) is in development. These reports should be available on the manufacturer’s website or upon request. GATEWAY demonstrations This program supports demonstration projects of high-performance SSL products. The purpose is to capture empirical data and experience with in-the-field applications that save energy, are cost effective and maintain or improve light levels. These provide a source of independent, third-party data for use in decision making by users and lighting designers. The GATEWAY Program staff suggests that this data be considered in combination with other information relevant to the particular site and application under examination (DOE 2010). To date, the GATEWAY Program has documented one museum application, at the Field Museum, Chicago, Illinois, in November 2010. Other museums are being considered, including several art museums. Since all GATEWAY Program museum reports can be downloaded online, this is a good place to start examining the issues you are likely to experience. Note that the evaluation questionnaire and the analysis of simple payback from the Field Museum have been adapted and included in the present Bulletin. Replacements for linear lighting (fluorescent lamps) Replacing fluorescent lamps with LED lamps rai
throughout the test. In practice, however, LED lighting systems are cycled on and off in almost all applications for both indoor and outdoor lighting. As has been demonstrated in the past, cycling lamps on and off has an impact on lamp life for other lighting systems such as high-intensity-discharge (HID) and fluorescent lamps. Although cycling may not have as dramatic an impact on LEDs, the driver electronics can be affected. Therefore, the TPC recommends that the burning cycle during lumen-maintenance testing should not be conducted in a constant on condition. Instead, the TPC specifies an operational cycle with certain periods of on time and off time. This cycling condition is intended to have a closer relationship to real-life LED system applications. Test duration The duration of testing is another variable to consider, and the area where experts have struggled the most to establish a standard. It is clearly understood that lumen maintenance over time usually cannot be detected over a short testing period. LM-80 specifies a minimum of 6000 hours of testing. However, for LED systems, including lamps, engines and luminaires, prolonged testing creates a large burden for manufacturers and the lighting industry. Any recommended testing procedure from the IES must present practical values for the duration of testing. A testing period that is too short may not lead to conclusive characteristics being identified. On the contrary, as stated above, a testing period that is too lon