Installation planning of Lighting: Three main types of artificial lighting installation are used in factories and offices, namely:
- Uniform general lighting
- General, plus local supplementary lighting
- Localized general lighting.
The choice depends on the natural and location of visual tasks to be performed.
Uniform general lighting
A uniform general lighting installation may be defined as one in which the fittings are evenly distributed throughout the whole interior, without any particular regard for the location of the work points in the room.
Typical application: Choice of lighting fittings Uniform general lighting is suitable in places where the work pints are, not fixed (e.g. foundries and large assembly shops, ware house, etc.)
Mounting height (Installation planning of Lighting):
General lighting units should be mounted as high as possible. This will reduce the risks of glare and improve light distribution throughout the interior .
The space between the units must not exceed a certain proportion of then mounting height above the work place. A reasonably uniform illumination level is important in installation of this kind, and the minimum value should preferably be not less than 2/3 of the average throughout the room.
General, plus local supplementary lighting:
In this system, additional local units (usually mounted close to the work point) supplement the evenly distributed general lighting provided by overhead units.
Typical applications: This system of lighting particularly suitable in places here a high level of illumination needed at a few definite location scattered about the room (e.g. When a shop mainly devoted to rough assembly work also contains on or two lathes).
Also, when light from the overhead installation cannot reach the work pint (e.g. inside the throat of a heavy power press)
As a general rule, the average level of illumination throughout the interior should not be less than the square root of the illumination level on the Locally lit work.
Localized general lighting (Installation planning of Lighting):
In this system, illumination wholly provided by overhead units of conventional type, which often (though by no means always) arranged in a regular pattern of the kind used in uniform generally lighting.
Typical applications: are space at irregular intervals throughout an interior, and in offices where correct placing of lighting units with respect to desks is of considerable importance in preventing troublesome reflections in ‘around the work.
When planning an office lighting installation an attempt should always made to light desks and tables from the side rather than from directly in front.
In drawing offices with horizontal boards, it particularly important to observe the principles outlined above.
When the boards are vertical however units are often; best arranged at right angles the window wall and parallel with the top edge of the board.
Work benches can lit in a number of ways; a few of which are show in, Slide-28 Hare arrangement (a) is generally the best; onto use when the work lies flat on the bench and the lighting fittings; hand low down with the edge of the shade below eye level. Arrangement (d) provides as particularly strong and shadow free form of lighting.
Artificial lighting in daylight offices (Lighting Systems in Industries):
It is not easy to lay down rules regarding quantity of illumination; also in this case the problem complicated by the fact that sky brightness; varies considerably from place to place from day to day. However, the following rule suggested as a rough practical guide.
Suggested minimum level of illumination:
When artificial lighting has to be used in large” daylight” office; where it is possible for people at the back of the room to see the distant window; workers in these remoter areas should have at least 50 lumen’s; per square foot (i.e. approximately 500 lux) on their work.