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Quartz Halogen Light Bulbs

Quartz Halogen Light Bulbs

Quartz halgen lights are incandescent lights, they operate by heating a thin wire. Halogen lights are much brighter than standard light bulbs but they are fragile and may easily burn out. Here we look at halogen lights, their design, why the burn out, what we can do to make them last longer and why we may consider replacing them with LED lights.

It is only when the power goes out that we realise just how important lighting is in our lives.

Last week I had a call from a woman with a problem. I very nice villa with 5 bedrooms and all the lighting provided by those rather nice little 50 watt halogen spotlights. The light is very attractive but the bulbs are continually blowing and are expensive to replace. Worse than that, each light has it's own transformer and these also burn out and have to be replaced.

This is costing a small fortune. Let us look at the design of light bulbs and what we can do to solve the problems of them blowing.

The first light bulb (or globe)

The first incandescent electric light was created in 1802 by Humphry Davy who passed an electric current through a strip of platinum. It didn't last long before the platinum disintegrated but it was a start. In 1841, Frederick de Moleyns patented a design using platinum wires contained within a vacuum bulb. In 1878 and 1880 Thomas Eddison patented improvements to electric lamps using carbon filaments. In 1904, Sandor Just and Ferenc Hanaman were granted a patent for a tungsten filament lamp. In 1913 Irving Langmuir found that filling a lamp with inert gas instead of a vacuum resulted in twice the luminous efficacy and a reduction of bulb blackening.

Incandescent light bulbs

Normal incandescent light bulbs consist of a tungsten filament within a glass bulb which contains an inert gas such as argon (if the bulb has oxygen in it the tungsten oxidises and very quickly burns out). An electric current is passed through the filament which heats up to between 2,000 and 3,300 °C, it gets white hot and emits visible light and a lot of heat.

At these temperatures the tungsten filament evaporates in use. The tungsten is deposited as black deposits on the glass. Eventually the filament will fail. Where the tungsten wire has small irregularities and is a little thinner, hot spots are created which increase the electrical resistance, the temperature and evaporation rate increase at that point and the filament fails more quickly.

The life of a light bulb is mostly determined by the presence (or rather the absence) of irregularities and thinner parts of the tungsten wire filament. Better quality bulbs have more consistent diameter of the tungsten wire and therefore last longer.

Halogen light bulbs

Those nice little halogen lightbulbs are a more recent development (1959). They also have a tungsten filament but within a small clear fused silica (quartz) bulb which contains an inert gas plus some halogen (usually iodine or bromine). These bulbs burn much hotter than standard incandescent light bulbs which is why quartz is used instead of glass to withstand the higher temperatures. They tend to emit a brighter whiter light. They also give out a lot of UV light and can give you sunburn.

As before the tungsten evaporates but, because of the halogen, rather than being deposited on the glass the tungsten vapour circulates within the bulb and is redeposited on the filament thereby extending its life. To support this regenerative cycle the voltage is important, the bulb must be hot enough to make the cycle work and not too hot or the filament will blow.

If the electrical supply is uniform and stable a quartz halogen bulb will last longer than a standard bulb. Unfortunately in places where the power is unstable voltage fluctuations and current surges cause these bulbs to blow.

Incandescent lights are very inefficient

Halogen lightbulbs are, like incandescent bulbs, very inefficient. Only 10 to 20% of the electricity consumption is turned into light, the other 80 to 90% is turned into heat. They use a lot of power and cost a lot in energy usage.

Halogen lights burn out very easily

The quartz glass gets very hot and must be installed very clean. If halogen bulbs are installed using bare fingers the natural grease that is deposited on the bulb will carbonise and result in overheating making them blow. If touched by bare skin they should be cleaned with alcohol.

These bulbs now come in 12 volt and 220 volt versions, the 220 volt type do not require 12 volt transformers however users report that these also blow just as often as the more common 12 volt variety.

Where you live makes a big difference. In some places the supply is far more unstable than in others. Commercial property nearby or the placement of transformer stations and switching gear can create irregularities and surges.

You may find that light bulbs often blow when they are first switched on. When cold a lightbulb filament has a lower electrical resistance than when it is hot so more current will flow through it. After about a tenth of a second the filament is hot and the electrical current falls to normal levels. This initial surge of energy as the bulb heats up has a tendency to blow filaments.

How to stop halgen light bulbs from blowing

So what we can you do to reduce the problem of quartz halogen light bulbs blowing?

  • Make sure the quartz glass is perfectly clean when installed, do not touch the glass of the bulb itself with your fingers. If contaminated clean the bulb with alcohol.
  • Only buy high quality bulbs (Philips tend to be best).
  • Only buy high quality transformers (Philips are the best, Osram medium quality and PS the lowest).
  • Install a voltage regulator to smooth out voltage fluctuations (evidence suggests that the power supply in Bali is now so variable that voltage stabilisers may not be fully effective).
    Install a dimmer on the lighting circuit, this can reduce the impact of voltage surges.
    Get your circuits checked. Wiring faults can cause sparking across terminals and create power surges.

Replace Halogen with LED lights

A far better option is to use different types of bulbs. Many people are removing their small quartz halogen spotlights and replacing them with energy efficient LED bulbs. The light may not be as attractive as that warm incandescent glow but the "Warm White" (as opposed to the stark mortuary like "Daylight White") is pretty good these days. LED bulbs use around a fifth of the electrical energy that incandescent lightbulbs use so they are much cheaper to run. Also they do not get hot and, more importantly, they don't have a filament that will blow all the time.

The technology of LED light bulbs is progressively improving and small spotlights and dimmer capable types are starting to become available. The saving on electricity bills is considerable, you will be doing your bit to help problems of power shortage and you will help the environment.

Copyright © Phil Wilson February 2009
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