The importance of lumen maintenance

A comparison of investment costs

Decisive for the standard-compliant operation of lighting systems are lumen maintenance and the LED failure rate. Comparing an ERCO high-performance LED (L90/B10) with a standard LED (L70/B50) demonstrates the positive effect of high-performance LEDs on investment costs. An office storey with a uniform matrix of luminaires consisting of 50 downlights serves as a reference. Light distribution is identical in both offices. The LEDs however differ with regard to lumen maintenance and failure rate. The analysis shows that reinvestments are inevitable in the long run with lower LED quality.

Standard LED module

Lumen maintenance: L70/B50 up to 50,000h
Failure rate: 0,2% of LED modules per 1,000h
This corresponds to a failure of 2 from 100 LED modules per 10,000h.

Standard LED module

Assuming identical maintenance factors, identical lighting values exist at the time of commissioning with use of standard LED modules. In reality though and due to the lower lamp luminous flux maintenance factor, a higher number of luminaires would be required to achieve the required maintenance values of the illuminance.
Em = 351 lx
U0 = 0.44

Standard LED module

With standard LED modules (L70/B50), significant reduction in luminous flux occurs after 10,000 operating hours. Furthermore, with 50 installed luminaires one downlight is expected to fail (failure rate: 0.2% of LED modules per 10,000h). Therefore uniformity falls below the normative specification of U0 > 0.4. The luminaire replacement therefore requires reinvestments over the operating duration.
Em = 323 lx
U0 = 0.45

Standard LED module

Due to the reduction of luminous flux with L70/B50, illuminance is only slightly above the recommended minimum value of 300lx after 20,000 operating hours. Because of the failure rate of standard LED modules (0.2% of LED modules per 1,000h), purchasing an additional luminaire cannot be avoided to compensate for the insufficient uniformity.
Em = 303 lx
U0 = 0.35

Standard LED module

Due to the failure rate of 0.2% of LED modules per 1,000 operating hours, with an installation of 50 luminaires the failure of one luminaire each 10,000 hours must be expected. Repurchasing individual luminaires is necessary to ensure that the uniformity of the normative recommendation of U0 > 0.4 is not fallen below.
Em = 323 lx
U0 = 0.45

Standard LED module

Due to the reduction of luminous flux with L70/B50, illuminance is again only slightly above the required minimum value of 300lx. The failure rate of the standard LED modules (0.2% of LED modules per 1,000h) again requires a reinvestment to compensate for the insufficient uniformity.
Em = 236 lx
U0 = 0.38