The issue of “maintenance” plays a significant role even when a lighting system is still on the drawing board. In industrial facilities in particular, malfunctions and the resulting replacement of lighting units while production is ongoing are associated with difficulties and high costs. 

Keeping this in mind, the lighting partner or architect needs to be increasingly aware of the maintenance issues, which impacts critically on the energy efficient lighting system. In determining this factor according to the “German Guidelines for Maintenance of Electrical Operating Systems” for interior spaces (CIE 97) and exterior spaces (CIE 154), the calculation is based on data for the Lamp Lumen Maintenance Factor (LLMF), the Lamp Survival Factor (LSF) and the Luminaire Maintenance Factor.

In addition, the Room Maintenance Factor (RMF) in interior spaces and the Surface Maintenance Factor (SMF) in outside spaces must be considered. Individual values should be indicated by the manufacturers directly or calculated. They always refer to an ambient temperature of 25°C, unless specified differently.

Naturally, the individual partial maintenance factors can never be higher than 1.0, and consequently neither can the resulting overall maintenance factor. Generally the result should be around 0.8 for interior spaces and 0.6 for outdoors. The rule here is: The higher the figure, the lower the necessary maintenance effort, while the result has to always be interpreted in relation to the optimum, which would be 1.

A maintenance factor of 0.8 for example results in having to oversize the lighting system by 25 percent, so that the necessary light flux of the lighting system can be guaranteed within a given time frame. In the context of industrial buildings, further specific criteria have to be taken into account and factored in: for example, the Room Maintenance Factor (RMF) is usually smaller than that for conventional interiors, as dirt in production halls tends to be much more frequent than in normal office spaces. Therefore, cleaning

of lamps and encasements has to happen sooner. In the summer especially, industrial buildings ( and this applies in particular under the ceilings, where lamps are installed) can get very warm. In this case, the figures for higher temperatures, separately quoted by the manufacturer, have to be considered.

In addition to this, lamps in production halls are subject to extreme strain as they are often constantly in use. For intense and longterm use in the industrial sector, TRILUX provides specific luminaires that have a longer rated lamp lifetime of 90,000 or even 100,000 hours, for example Mirona or Nextrema, which in addition to this can also be used in wet rooms. Further information concerning the determination of a maintenance factor can be found in the “German Guidelines for Planning Security in LED Lighting” issued by ZVEI.