Originally, low-voltage halogen light fittings were developed for illuminating commercial premises. Being small and unobtrusive, they blend into any scheme and the bright intense beams of light they produce are ideal for display lighting. The potential for dramatic effects and narrowly focused task lighting was not lost on home owners, and manufacturers were quick to respond with a range of low-voltage fittings.
The specially designed miniature bulb is the key to what makes low-voltage lighting so attractive. The light source is concentrated into a small filament, which enables accurate focusing of spotlight beams. The integral ‘dichroic’ reflector allows the heat generated by the filament to escape backward into the fitting, creating a cool but intense white light. Coloured bulbs are also available for special effects and mood lighting.
Low-voltage light fittings
Miniature fixed or adjustable ‘eyeball’ downlighters recessed into the ceiling are among the most widely used low-voltage light fittings. They can be mounted individually or wired in groups to a transformer, which is also concealed in the space above the ceiling. Some fittings are made with integral transformers; these include table lamps and small spotlights.
Others, such as track lights, combine several individual fittings connected to a single transformer. Unique to low-voltage lighting are fittings connected to exposed plastic-sheathed cables suspended across the room.
Even a small increase from the designed voltage can halve the life of a bulb. If the voltage is too low, light output drops and eventually the bulb blackens. Voltage can be affected in a number of ways, and you need to select your equipment accordingly.
Choose a transformer with an output that closely matches the combined wattage of the bulbs on the circuit. It’s important to ensure that the total wattage of these bulbs is greater than 70 per cent of the transformer rating, or the bulbs will burn quickly. For example, a 50W transformer can supply two 20W bulbs or one 50W. A 200W transformer is perfect for four 50W bulbs, but not for six 20W bulbs (for these, you would want a 150W transformer). If you buy a low-voltage kit, you can be sure the transformer is suitable. Even with a perfectly matched transformer, replace a blown bulb as soon as possible to avoid overloading the other bulbs on the circuit.
Using ordinary dimmer switches is not advisable, because they too reduce voltage to an unacceptable level. For this type of control, check that the low-voltage fittings are suitable for dimming and only use dimmer switches specifically designed for low-voltage lighting.
Using separate components
If you install a low-voltage lighting kit that comes read wired (see opposite), there is no need to notify your Building Control Officer except when it is fitted in a special location such as a kitchen or bathroom. However, if for some reason it is not convenient to use this type of kit, it is possible to install low-voltage lighting, using individual components such as light fittings, transformer and cable. However this type of work is notifiable.
Having decided on the ideal location of each light fitting choose a central position for the transformer. However, on the low-voltage side, use a separate 1.5mm2 two-core cable for each light fitting, keeping this as short as possible -a maximum of 4 metres from each
fitting to the output terminals of the transformer. Normally, each light fitting is supplied with a terminal block for connecting its heat-resistant flex to the cable.
If necessary, you can install longer cables to each light fitting, but this would involve calculating the larger cable sizes required.
If you are interested in fitting low voltage lighting in your home why not give Colchester Castle Electrician a call on 01206 700769.
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Colchester Castle Electrician providing electrical services for customers in and around Colchester, Essex.