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SJE Electrical Installations
Lighting Techniques:
Types of fittings. Fittings should be chosen according to their
qualities in the following respects: appearance; light distribution;
brightness; ease of erection, relamping and cleaning; cost; and
luminous efficacy. The order of importance changes with different
applications, but light distribution should always be considered
first.
Fittings classed 'mainly direct' give most of their light in one
direction. With any given type of lamp they will give the highest
luminance per watt of electrical input, with some likelihood of
glare either direct from the lamp or by reflection from polished
working surfaces, with a tendency to hard and deep shadows, but with
the possibility of ensuring that at any particular working position
most of the light comes from the desired direction as may be
required in say a drawing office.
Direct lighting is almost always used for industry and for display
purposes in shops; it gives a brisk, lively effect which emphasizes
light and shade and reveals shape well.
Indirect lighting is usually considered more restful and is used
mainly for restaurants, hotels and other social interiors, and in
combination with direct lighting for many classes of shops although
it is becoming increasingly popular for office lighting using
so-called 'uplights' fitted with SON-DL or MBIF lamps. 'General
diffusing' lighting, or 'direct' is generally used in offices and
schools.
Spacing of fittings. In most interiors which contain several
lighting fittings the aim is usually to provide general lighting, a
comparatively even illumination at working level all over the room.
This allows furniture and plant to be moved and added to without
altering the lighting installation. Too wide a spacing of fittings
would give the effect of comparative darkness between pools of
light, whereas an unnecessary close spacing would be uneconomic.
As a general rule, applying both to fluorescent lamp fitting and
other types normally used for general lighting, a satisfactory even
illumination results when the fittings are not spaced more than 1 x
times their distance above the plane of work, with end fittings half
the distance from the wall, or one-third, if work is done next to
the wall.
Floodlighting Techniques
This form of outdoor illumination has three main applications,
(a) for industrial purposes, (b) for decorative purposes, and (c)
outdoor sports
Industrial floodlighting. High-pressure discharge lamps are suitable
for this type of application. The SON lamp for example, is commonly
used area floodlighting and SON.TD or MBIL/H or lamps used in
accurately designed parabolic reflectors are also used for long
distance floodlighting.
Decorative Floodlighting. It is necessary in this application first
to decide upon the average illumination required. This naturally
depends on the reflection factor, which depends on the texture of
the surface and whether it is clean or dirty. For clean Portland
stone the factor is 60%, which is reduced to 20% if the surface is
dirty. On the other end of the scale clean red brick has a
reflection factor of 25%, dropping to 8% if dirty.
The question of arranging the projectors requires careful
consideration. Lighting directly from the front is seldom
satisfactory, while lighting from an angle can be most pleasing.
Lighting of polished surfaces is seldom successful using
floodlights, as they tend to act as plane mirrors, producing an
image of the floodlight.
One technique is to light objects in front of the polished surface
so that it stands out in silhouette.
Sports grounds. Practice or casual training areas can be lit from
one side by using tungsten halogen lamps, mounted on 3-5 metre poles
but tournament areas require a higher luminance and more rigorous
glare control. Minimum mounting heights of 10 metres are recommended
and the area should be lit from both sides.
Stadiums are lit to a higher standard. The most popular method is to
light the area by means of 1000W SON or similar, deluxe lamps
mounted on towers up to 30 metres high.
Garden lighting grows in popularity
A garden can come to life in the evening with just a few, carefully
selected fittings. Outdoor lighting can extend the use of outdoor
space while providing safety, security and peace of mind. Garden
lighting continues to grow in popularity as more and more homeowners
want to link outdoor living with the comforts of the home. You can
turn your garden into an inviting and attractive haven with a little
imagination and the right ingredients.
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