The maintenance factor affects energy consumption

The new standards give light planners greater responsibility for the system, as the installation’s maintenance factor has a direct effect on the energy consumption.

To select a high maintenance factor a great deal of care must be exercised when choosing light sources, luminaires and the lighting system. The choice of T5 luminaires gives the best conditions for achieving a high maintenance factor.

For further information on calculating the maintenance factor, refer to the SLL Code for Lighting.

Table 5.1 Quick reference card to determine the maintenance factor

The lighting installation’s maintenance factor for an open luminaire with a 3 year cleaning interval and with clean surroundings.
The light source’s
light depreciation
after 10,000 h
Examples of light sources Light depreciation factor
≤ 10 % Straight fluorescent lamps with barrier layer for low light depreciation and high pressure sodium lamps. 0.85
10–25 % Other fluorescent lamps, compact fluorescent lamps and mercury lamps, LED. 0.80
≥ 25 % Metal halide lamps. 0.70

 

Table 5.2 Proportion of the maintenance factor formed by the light source’s light depreciation

 

The light source’s
light depreciation
after 10,000 h
Examples of light sources
Light depreciation factor
≤ 10 % Straight fluorescent lamps with barrier layer for low light depreciation and high pressure sodium lamps. 0.90
10–25 % Other fluorescent lamps, compact fluorescent lamps and mercury lamps, LED. 0.85
≥ 25 % Metal halide lamps. 0.75

 

Table 5.2 is an adaptation of CIE 97:2005 2nd Edition to local conditions. If other factors are used, the method by which these have been calculated must be reported. For more accurate information on factors for luminaires and light sources, contact your supplier.

 

Table 5.3 Proportion of the maintenance factor corresponding to the contamination of the luminaire, taking into account the luminaire type, surroundings and cleaning interval 

Number of years between group cleanings
2.0
3.0
4.0
5.0
Luminaire type Surroundings Surroundings Surroundings Surroundings
  Clean Dirty Clean Dirty Clean Dirty Clean Dirty
Open luminaire 0.96 0.85 0.94 0.77 0.92 0.72 0.9 0.66
Closed luminaire 0.98 0.87 0.96 0.84 0.94 0.78 0.92 0.71
Indirect uplight luminaire 0.91 0.68 0.84 0.54 0.77 0.40 0.71 0.29

 

Tables 5.2 and 5.3 must be used together to calculate a maintenance factor. Normal formula for maintenance factor = LLMFxLSFxLMFxRSMF (see explanation on the page of Quantities, units and their meanings).

 

Example

  • Closed luminaire for fluorescent lamps
  • Clean environment
  • 2 years between group cleanings
  • Maintenance factor = 0.90×0.98
  • Total maintenance factor 0.88

 

Application area