As with other light sources, the luminous flux of LEDs decreases over time so that from a certain point the illuminance originally required is no longer achieved. The reliability and efficiency of LEDs depend largely on its operating conditions. ERCO luminaires therefore are thermally designed to remain below the critical temperature range when properly operated to ensure maximum luminous flux over a long life.
Since total failure of an LED is very rare, LEDs are more accurately defined by using the lumen maintenance factor over a specific period of time. As a blanket value it is common practice to indicate the time after which the luminous flux for a specific percentage of all LEDs has reduced to 70%, 80% or 90% of their original luminous flux.
The standard specification of LEDs currently used in the market is L70/B50 50,000h, i.e. after 50,000 hours, only 50% of the LEDs used still achieve 70% of their original luminous flux.
L and B values
The L value represents the percentage of original luminous flux that the LED continues to achieve after the specified number of operating hours. If no B value is indicated, B50 should always be assumed. By definition, the B value reveals nothing about the total failure of an LED. It indicates the percentage of LEDs that fall below the L value after the specified number of operating hours.
As a benchmark, the operating hours are always indicated together with the L and the B value. Based on the LM-80 method, ERCO LEDs are measured over a minimum of 8,334 hours and extrapolated to 50,000 hours using the TM-21 method. The operating hours may be extrapolated to a maximum of six times the actual time measured.
LEDs used at ERCO
ERCO uses highperformance LEDs with the specification L90/B10 50,000h, i.e. up to 50,000 hours, at least 90% of the LEDs still achieve 90% of their original luminous flux. This said, the remaining 10% of the LEDs will not have failed but continue to achieve up to 89% of their original luminous flux.