Constant Light Output (CLO)
As LEDs are used, their light output degrades. This light decrease is more or less linear across the lifespan of the LED. The luminaire itself can compensate for this light decrease using a programmable driver. This is known as Constant Light Output (CLO), or constant luminous flux, indicated by L100.
The benefit of CLO
Fagerhult’s CLO luminaires with L100 maintain the same light level after 50,000 hours of burn-time as when they are first switched on. CLO luminaires with L100 provide a higher maintenance factor, which is positive because this enables more optimised systems. The optimisation is made possible by reducing over-lighting. Less over-lighting means less installed output and, in some cases, can even mean fewer luminaires.
How does a luminaire get CLO?
CLO is possible by pre-programming the power supply to increase during a specified time. Thus, the increase in power compensates for the LEDs’ light depreciation.
Calculating the maintenance factor
In the example, we calculate the maintenance factor using the L-value of the luminaire at 50,000 hours. We have a suspended luminaire and use values for an open luminaire and a three-year cleaning interval. The maintenance factor is calculated by multiplying light depreciation, lamp survival factor, luminaire maintenance factor and room surface maintenance factor. The method for calculating the maintenance factor is provided in the Swedish template Ljusamallen, which also stipulates the values to be used for different environments and luminaire types. In the last row, we see that the L80 luminaire has a maintenance factor of 0.71, while the luminaire with CLO and L100 has 0.89.
| L80 | L100 | |
| Light depreciation (LLMF, Lamp Lumen Maintenance Factor) | x 0.80 | x 1.00 |
| Lamp Survival Factor (LSF) | x 1.00 | x 1.00 |
| Luminaire Maintenance Factor (LMF) | x 0.94 | x 0.94 |
| Room Surface Maintenance Factor (RSMF) | x 0.95 | x 0.95 |
| Maintenance Factor (MF) | 0.71 | = 0.89 |
Installationsexempel
Exemplet visar ett kontorslandskap med pendlade armaturer (ren miljö med tre års rengöringsintervall) där nyvärdet kan dras ner till 562 lux tack vare CLO-armaturer med L100. Det lägre nyvärdet är möjligt eftersom att CLO-armaturer med L100 ger anläggningen en högre bibehållningsfaktor.