The maintained value of a lighting installation is calculated using the light output ratio and the luminaire maintenance factor specified for the luminaire.
According to DIN/EN 13032/2, the LOR (Light Output Ratio) describes the ratio of the luminous flux of the luminaire to the lumens of the lamps used. Luminaires with direct/indirect emission also specify the "DLOR" (Downward Light Output Ratio) and the "ULOR" (Upward Light Output Ratio) as separate components. These indicate the light intensity distribution of a luminaire in the lower and upper parts of the room.
The luminaire maintenance factor LMF takes into account the reduction of luminous flux due to the spoiling of the luminaire. It signifies the ratio of a luminaire’s light output ratios before and after cleaning. The LMF depends on the version of the luminaire and the related possibility of soiling. The luminaires are classified by their "maintenance factor according to CIE".
ERCO Newsletter - inspiring projects, new products and fresh lighting knowledge