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    Lighting


  • Lighting

    Lighting is of critical importance in buildings. An adequate level and distribution of light is vital if visual tasks are to be carried out safely and effectively. Good lighting will also improve the internal environment and appearance of a building. Lighting should be used to supplement daylighting, which makes the design, planning, and functionality of lighting one of the most important elements when building. Lighting also needs to be efficient and cost effective. The use of efficient lamps, ballasts and luminaires with appropriate lighting controls, can provide the right visual environment, be energy efficient and cost effective, as the cost of electricity becomes more and more expensive. As with any design related project, the budget is central to the design. This is usually established by applying a certain percentage of the overall building budget towards the “architectural professional”. It used to be accepted that lighting should constitute approximately 2 to 3% of the total budget. However, all too often budgets allowed for lighting are extremely low and inadequate, again highlighting the need for proper planning. Today, the suggested budget for lighting should be in the region of 4 to 5%.

    It is possible to save enormous amounts of electricity over long periods of time with energy-saving lamps. Fluorescent lamps are now more compact, kinder to the environment and offer better colour rendering. You can drastically reduce energy consumption with innovative lighting solutions such as CFLs and LEDs, which have an extremely long life and contain no hazardous substances, or with lighting that can be dimmed as required.

    A few simple guidelines to help get your lighting right:-

     

            • Decide what the lighting is needed for, and then design your lighting scheme to position lights where they will be used. Use functional lighting and provide sufficient plug sockets for reading lamps.

     

     

     

            • Use only lamps appropriate to the luminaire (see lamps later in section).

     

     

     

            • Light for safety and security.

     

     

     

            • Light for effect. Reduced background lighting levels create more contrast in a room and can save energy.

    Lighting Terminology
    Ballast/control gear
    Apparatus to start and control the current through fluorescent and other discharge lamps.

    Diffuser
    A translucent screen used to shield a light source and at the same time, soften the light output and distribute it evenly.

    Discharge Lamps
    A lamp whose illumination is produced by an electric discharge through a gas (neon), or a metal vapour (mercury, sodium), or a mixture of gases and vapours.

    Efficacy
    A measure of the effectiveness of a lighting installation in converting electrical power to light (lumens/watt).

    Lumen
    A unit of luminous flux used to describe the amount of light given off by a lamp.

    Luminaire
    The term for a light fitting, Luminaire distributes light from a lamp and includes all components for fixing, protecting the lamps and connecting them to the electricity supply.

    Lux
    Unit of illuminance, or amount of light on a surface (lumens/m2).

    LED
    Light-emitting diode.

    Lamp
    Commonly known as a light bulb.

    CFL
    Compact fluorescent lamp.

    Colour Rendering Index (CRI)
    CRI is a comparison of a light source’s ability to accurately render the colour of an object to that of a standard reference light source? The CRI scale is from 0 to 100, with a value of 100 indicating excellent colour rendering. Sunlight and most incandescent lamps have CRI values of 100. Only compare the CRI values of light sources of roughly the same colour temperature.

    Colour Temperature
    Colour temperature is a way to compare the colour of light from different types of lamps. It is often referenced as cool (slightly blue) or warm light (slightly orange). Incandescent lamps and candles give off warm colour temperatures, while sunlight and some fluorescent lamps emit cool colour temperatures.
    Efficacy is a measure of light output (lumens) per Watt of electrical power needed by the lamp. Lumens measure how much light is emitted. Watts indicate how much electrical power is consumed.

    Lighting Principles
    When designing or planning lighting, ensure that light is directed to where it is needed. Heavy shadows can be avoided if the light is properly positioned and there is adequate contrast. Often, a whole room is lit to a bright level, or even the whole house is lit, and yet a person is working with barely enough light for the task at hand, e.g. reading, writing or preparing food. In general, lighting layouts should avoid creating a situation where all lighting has to be switched on to illuminate one part of a room, e.g. lights furthest from windows should be switched on independently from those closer to windows. Lighting equipment comprises a lamp, ballast, control gear or transformer if needed, and the luminaire (light fitting). Each element contributes to the overall efficiency. There is no sense in placing an efficient energy saving lamp in an inefficient luminaire, or an efficient combination of lamp and luminaire in an inefficient position. It is, therefore, imperative to choose the combination that is most efficient for the position and purpose.

    Artificial lighting can be categorised in the following three groups:

     

              1. General, e.g. a central hanging light;

     

     

     

              1. Functional or task, e.g. wall mounted picture light or a table lamp; and

     

     

     

              1. Decorative, e.g. ornamental wall light or lighting used for effect.

    The light must have the right illuminance, it must be uniform and glare-free, and it must have an excellent colour rendering to avoid fatigue and eye-strain e.g. a soft light that is not too bright is needed for a relaxing mood, while for reading you need luminaires that offer a small pool of bright light. Wardrobe and dressing tables can be attractively lit with halogen or LED light.

    Illumination Levels
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    Regulations for Lighting

    Lighting installations in new dwellings and buildings, to be served by artificial lighting, should comply with the lighting requirements of SANS 10142: The wiring of premises Part 1: Low-voltage installations.

    These regulations set out standards of energy efficiency, and provision of lighting controls. The only other standards regulating luminaires are as follows:-

     

            • SANS 60570/IEC 60570: Electrical supply track systems for luminaires.

     

     

     

            • SANS 60598-2-18/IEC 60598-2-18 (SABS IEC 60598-2-18), Luminaires: Part 2: Particular requirements – Section 18: Luminaires for swimming pools and similar applications.

     

     

     

            • SANS 60598-2-23/IEC 60598-2-23 (SABS IEC 60598-2-23), Luminaires: Part 2-23: Particular requirements – Extra low voltage lighting systems for filament lamps.

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    The CFL is a miniature version of the standard, well-known fluorescent tube, and was developed as a replacement for the less efficient tungsten filament lamp (incandescent).

    There are two types of CFL:-

     

            • Plug-in CFLs have an integral ballast and can be used as a direct replacement for tungsten filament lamps as they can be plugged into the same lamp holders.

     

     

     

            • 2-pin and 4-pin CFLs require a separate ballast.

    CFLs will save most energy when used in fittings that are switched on for more than four hours per day. CFLs last about eight times longer than tungsten lamps and use as little as 25% of the energy used by tungsten lamps for an equivalent light output.

    Although it is an alternative to the tungsten lamp, a CFL has different characteristics that users need to be aware of:

     

            • Dimming requires special control gear; low energy lamps take a few seconds longer to light up.

     

     

     

            • Those with HF ballasts light up instantly and quickly become bright.

     

     

     

            • Mains frequency types take longer to start and reach full brightness.

    The colour rendition of CFLs has been improved and now produce an almost identical effect to that of tungsten’s. The ‘warm’ white CFL lamp is closest to the tungsten lamp, ‘medium’ white or ‘cool’ white give a progressively bluer light.

    There are a large number of ceiling and wall-mounted exterior bulkhead fittings for CFLs. Since extreme temperatures can affect the light output from CFLs, fittings should be chosen that are well insulated, and wherever possible, operate the CFL with lamp cap down (the cap produces heat that then rises to warm the whole lamp, leading to a more efficient operation). The majority of bollard light fittings currently available are designed to take CFLs or other high-efficacy lamps.

    Special dimmer switches using an electronic dimming ballast can be used to dim 4-pin CFLs. At present, none of the available plug-in CFLs with integral ballasts are suitable for dimming.

    There is an increasing range of fluorescent lighting. Some significant advances are:

     

            • Slimmer tubes that use less electricity to deliver the same light output.

     

     

     

            • Improvements in the colour rendering quality of lamps.

     

     

     

            • High-frequency (HF) control gear that saves energy, eliminates the familiar flicker associated with fluorescent tubes, and extends lamp life.

     

     

     

            • Fittings with better optic designs that direct a higher proportion of the light produced by the lamp into the room, thereby reducing the number of lamps needed.

    Slimline 16mm (T5) tubes should be used for new installations, as they give higher efficacy and reduce luminaire size. HF ballasts for fluorescent tubes, although more expensive, avoid flicker and provide additional energy savings of 15–20%. Dimmable HF ballasts are available.

    For task lighting or spotlighting, tungsten halogen lamps are commonly used. They are mainly for indoor use and are relatively cheap to buy, but have high running costs. They are 50–100% more efficient than standard type bulbs and last about twice as long. Tungsten halogen lamps are not recommended for general lighting and up lighting because they use more energy than fluorescent lamps. Many tungsten halogen lamps operate at 12 V and require a transformer.

    SON lamps are the main choice for external lighting because of their very long lamp lives (typically 14 000 to 24 000 hours) and low electrical consumption. However, the lamps give a yellowish light but the SON Deluxe lamps (improved SON lamps) have a golden white light. SOX lamps are the most efficient light source available, but they have poor colour rendering properties. SOX lamps have a strong yellow light, familiar in street lights, and a shorter lamp life than SON lamps.

    Metal halide lamps give excellent, crisp white light and have low energy consumption with a lamp life of about 6000 hours, while being about three times that of tungsten halogen lamps, is much shorter than SON lamps. Lamp replacement costs are therefore higher than for SON or SOX lamps. However, these lamps have better colour rendition than SON lamps and can be used indoors or outdoors. There are smaller wattage lamps that are useful for display lighting.

    LED technology in lighting has come a long way in South Africa over the past few years, providing very low energy consumption. These lamps cost more to purchase but outlast conventional by a long way. They also save energy and, therefore, money. LEDs are now manufactured in different shapes to suit past installation, e.g. golf ball, candle, down lighters, spot lights.

    Luminaire Types
    The following information is intended to illustrate the types of fittings available and the categories to which they are classed. The product range per category is too vast to cover in this publication. Further detail of product choice, range and specifications are contained in product literature available through manufacturers, distributors and light fitting merchants. A visit to an established light fitting showroom will provide the reader with an indication of what products are available per category listed below.

    Lighting Tips

     

            • With multiple light sources, you can create pools of light and give structure to a room.

     

     

     

            • Indirect lighting adds height to a room.

     

     

     

            • Create different moods with different light sources. Recessed furniture light turns shelving and cabinets into real eye-catchers.

     

     

     

            • Avoid beam angles that are excessively narrow so people around the table are not in shadow (desk, dining etc.).

     

     

     

            • Luminaires integrated in furniture provide light precisely where it is needed.

     

     

     

            • You can create different lighting moods with dimmable luminaires.

     

     

     

            • Indirect light creates a pleasant glare-free atmosphere.

     

     

     

            • Provide adequate lighting over work surfaces and ensure the luminaires are positioned correctly to avoid working in your own shadow.

     

     

     

            • Lamps positioned to the left and right of a mirror prevent annoying shadows falling on your face.

    What is Induction Lighting?

    An electrodeless lamp or induction light is a light source in which the power required to generate light is transferred from outside the lamp envelope to inside via electromagnetic fields, in contrast with a typical electrical lamp that uses electrical connections through the lamp envelope to transfer power.

    There are three advantages of eliminating electrodes:-

     

            • Extended lamp life, because the electrodes are usually the limiting factor in lamp life.

     

     

     

            • The ability to use light-generating substances of higher efficiency that would react with metal electrodes in normal lamps.

     

     

     

            • Improved collection efficiency because the source can be made very small without shortening life, a problem in electroded lamps.

    Information supplied by Buildaid Publishing.

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