If the efficiency gains from limiting the operating time of the lamps are to be realized, it is important that both the building occupants and maintenance personnel understand the benefits of using the occupancy sensors or other lighting controls. One of the most important activities that can be performed on a lighting system is programmed maintenance. From the moment that a lighting system is installed, its performance declines. The light output from the lamps decreases as the lamps age. The lenses discolor, decreasing light output.
Dirt accumulates on lamp and fixture surfaces, further decreasing light output.
The net result is a decrease in light output with no decline in energy use. Without programmed maintenance, this light output will continue to decline and will result in areas being underlit. Building occupants, in response to these underlit conditions, may decide to bring in their own task lighting, which may well have a lower operating efficiency than the primary lighting system. As a result, overall lighting system efficiency decreases while energy use rises. Group Relamping Most facilities still replace lamps on a spot basis as they burn out.