In recent years LEDs have gained popularity not least of all because they are sleek, emit little heat and have a broad colour spectrum. But there can be huge differences in quality amongst the immense range of products available.

This is why in November 2013 standards were outlined for LED lights. In its “LED Lighting: Guidelines for Safer Planning”, the German Electrical and Electronic Manufacturers’ Association (ZVEI) recently set out standardized criteria to enable an objective comparison of LED solutions, and allow fair competition. In compiling the guidelines, technical parameters such as performance, lumen intensity, light yield, light intensity distribution, colour quality, ambient temperature and service life all played a large role.

For planners not just light intensity, light colour and consumption are important, as above all service life and the maintenance factor are key factors. LEDs are classified according to luminous flux behaviour and service life, and the factors service life, degradation and total failure are observed. These factors are labelled with the letters LxByCz. Lx refers to the service life, (e. g., 50,000 h), for which a certain percentage x of the original luminous flux is achieved when new. By describes the

percentage of LEDs, which at the defined end of service life fall below the aspired luminous flex of x percent (Lx). Cz describes the percentage of LEDs that experience total failure. So if we take an LED labelled L80 B10 C0 – 50,000 h this indicates that only 10 percent of the LEDs that were previously intact at the end of their service life of 50,000 hours supply luminous flux of less than 80 percent of their initial brightness.

If no B figure is given, the classification is B50, which means that the drop in luminous flux applies to half the LEDs. In the example given above there would have been no total failures (C0) by the end of the service life). Manufacturers are asked to classify their LEDs according to the ZVEI guidelines so that in future architects and planners can take total failure of LEDS into account.

If the figure is worse than L80 B10 this can mean that in planning new facilities 15 percent more lights have to be calculated to offset the shortfall in luminous flux.