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Lighting design
Calculation of room index

a
Length

b
Width

hu
Useful height (between luminaire and work surface)

After calculating K, find utilisation factor U (real efficiency) on photometric data sheet table 8 based on room reflection.
See the table below for reflection values.
Calculation of luminous flux

E
Average illumination (lx) required from system.

A
Surface area (m²) of room.

U
Utilisation factor.

P
Product of maintenance factors due to dust accumulation on luminaire and lamp aging.

The maintenance category for dust on the luminaire is indicated on the photometric data sheet table 5 and values in diagrams cat. I, II, III, IV, V, VI shown below.
Aging of the fluorescent lamp is measured by the mean depreciation curve shown below.
Calculation of number of luminaires to be installed

f
Total luminous flux (lm) of lamps installed in the luminaire.
Lighting uniformity

For best uniformity, do not install the luminaires beyond distances Dt and Dl recommended in photometric data sheet table 2.
Reflections in % of painted surfaces and materials (ceiling max 85%; walls max 50%; floor max 30%).
Maintenance factors due to dust accumulation and lamp aging.