"Nice Lights But ......."
I used to have a great pembantu, by great I mean she was not so much famous as large. Unlike most rather petite Indonesians Sri was the sort of person who was handy to have around if you had a ship to rivet or perhaps the odd horse to shoe. She was very useful to take to the pub for arm wrestling competitions.
She was not only strong but assertive as well. Well do I remember the time when I was tentatively wangling a barbecue out of the back of my car, a casual nudge in the ribs that moved me a metre to the left was her polite way of saying “excuse me, could I trouble you to please move aside.” She lifted that thing out of the car faster than a president dodging a well aimed shoe.
But sadly the great Sri moved on to where most good pembantus go – motherhood.
One night a far more lightly built young woman was attempting to change the water gallon and, as usual, I stepped forward to do the heavy lifting. Fumbling around with a plastic bottle full of sloshing water I got to that point of no return, you know what I mean, the moment when you let the thing go and you are committed, the bottle is on its way into the water dispenser and nothing will stop it. The towel around my waist is starting to fall off and suddenly - pop! The power goes out and I am in total darkness trying to control a wobbly falling bottle while grabbing at a wardrobe failure.
“Oh dear” I quietly say to myself.
I am instantly reminded of how incredibly useful an electric lightbulb can be. My unexpected blackout is simply one of the everyday small inconveniences of living in the very nice place I live but where small creatures like to chew electric cables. I don't know why they do it, perhaps they get some kinky orgasmic pleasure as their teeth short out the live and neutral and their little tails straighten out somewhat.
Unfortunately for many the instant loss of light is an everyday occurrence and more usually caused by blown lightbulbs.
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 and she is not alone. Small quartz halogen spotlights have become very popular and all over Bali people are climbing stepladders to change lightbulbs. A continuous stream of containers rumble their way across Indonesia delivering halogen lightbulbs to villa owners in Bali.
Let us start with how a light bulb works.
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, Sándor 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.
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 lots and lots 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.
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 Bali the supply is very unstable and voltage fluctuations and current surges cause these bulbs to blow.
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.
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. I have spoken to a number of people whose lightbulbs seldom fail.
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.
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.
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 compact fluorescent 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. Compact florescent 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 compact fluorescent 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 PLN's problem of power shortage and you will help the environment.
Oh dear, the gallon is empty again.
Copyright © Phil Wilson 2009
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