Working life of LED luminaires
When we talk about “working life”, we are talking about the value at which the luminous efficacy of the luminaire decreases below a minimum threshold, not until it stops shining completely. According to international standards, the working life of LED luminaires must be stated with two declared values: the expected light depreciation for LEDs (L-value) and the theoretical lifetime of the driver. These values must be calculated to determine the working life of a luminaire.
What affects the working life of a luminaire?
The expected working life of a LED luminaire is affected by several factors:
- LED type and model
- The level of current powering the LED
- The type of driver used
- The construction of the luminaire (temperature can impact sensitive electronics)
- The environment and ambient temperature where the luminaire is installed.
LED — calculated light depreciation (L-value)
The L-value describes the expected light output as a percentage of the initial value when the specified time has been reached. The L-value is combined with an expected use time or burn-time depending on the application. L-values are stated at fixed hours corresponding to the most common applications: 35,000h, 50,000h, 75,000h, and 100,000h. All L-values are median values, i.e. equal above and below. Times longer than 100,000 hours are not declared.
A value of L100 / 100,000h means that the luminaire has no light depreciation during the time. A value of L96 / 50,000h means that the luminaire provides 96% of the initial luminosity after 50,000 hours. Times longer than 100,000 hours are not declared.
The expected light depreciation is calculated using the TM21 method, where the input data comes from the LM80 data provided by the supplier of the LED. In cases where LM80 data cannot be used for a reliable calculation, the LED suppliers’ internal calculation methods can be used.
We follow recommendations from LightingEurope
LightingEurope publishes recommendations in the guiding paper titled Evaluating Performance of LED Based Luminaires. The lighting industry in Sweden has agreed to follow these recommendations. The recommendations are published in Ljusamallen, of which one version is for the comparison of indoor lighting calculations, and the other for comparison of indoor LED luminaires. Current versions are available at ljuskultur.se.
You are always welcome to contact us with any questions or for more information. Please, reach out to your Fagerhult contact person.
Theoretical working life of LED drivers
The driver’s working life is affected by the containing electronic components, its design, and temperature. Drivers have a temperature reference point (TC). When testing luminaires, the temperatures at the point of TC are measured and compared to the data provided by the manufacturer for the estimated working life. The lower the temperature, the longer the expected working life. For the luminaire, the driver working life is stated in hours together with the expected maximum loss during this time, for example 50,000h/10% or 100,000h/10%.