Maintenance factor Absorption factor,Reflection factor,�Co-efficient of utilization

Discussion about Maintenance factor Absorption factor,Reflection factor,�Co-efficient of utilization

1. Maintenance factor,Absorption factor,Reflection factor, Co-efficient of utilization Presented by Suhail TP MES Collage of Engineering 1 ELECTRICAL SYSTEM DESIGN

2. Maintenance factor In lighting calculations, ratio of illumination of a light source or lighted surface at a given time to that of initial illumination. This factor is used to determine depreciation of a lamp or a reflective surface over a period of time. MF:Ratio of illuminance at end of maintenance period to initial illuminance. 2 ELECTRICAL SYSTEM DESIGN

3. Maintenance factor( contd )… Dust & dirt of surroundings may get deposited on light fittings & hence deteriorate lamp efficiency. If regular periodic cleaning is adopted & assuming good atmospheric conditions ,value of maintenance factor may be taken as 0.8 3 ELECTRICAL SYSTEM DESIGN

4. Maintenance factor( contd )… For dusty & dirty atmosphere, factor may be as low as 0.4. Another term depreciation factor is also used which is reciprocal of maintenance factor. Depreciation factor=1/(maintenance factor) 4 ELECTRICAL SYSTEM DESIGN

5. Reflection Factor & Absorption factor Whole of the light incident on a reflecting surface is not reflected. Some portion of it is absorbed by the surface. The ratio of reflected light to incident light is called reflection factor . The ratio of absorbed light to incident light is called absorption factor. 5 ELECTRICAL SYSTEM DESIGN

6. Co-efficient of utilization The lumen output of sources is not fully utilized at work place. Part of it is lost in fittings. Some part is directed to walls & ceiling which may be absorbed or reflected. This is taken into account by a factor known as co-efficient of utilization 6 ELECTRICAL SYSTEM DESIGN

7. Co–efficient of Utilization( contd …) A surface to be illuminated receive light either directly from lamps or reflected from ceiling & walls or both. In this case, total flux reaching the surface will never be equal to flux emitted by lamp, due to absorption by reflectors, ceiling & walls. Utilization factor = lumens reaching at the working place total lumens emitted by the source Usually it varies from 0.5 to 0.8. 7 ELECTRICAL SYSTEM DESIGN

8. Co–efficient of Utilization( contd …) Co-efficient of utilization depends on L umen output of fitting Size & shape of room R eflection factors of walls & ceiling Height of ceiling Arrangement of fittings. 8 ELECTRICAL SYSTEM DESIGN

9. Calculation of Illumination Where N=Number of fittings needed. E=Required Illumination(lux). A=Working area( sq.m ) O=Luminous flux produced per lamp(lumens) CU=Co-efficient of utilization. MF=Maintenance factor.   ELECTRICAL SYSTEM DESIGN 9

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