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I have a strip of 3 downlights in my living room, and I am constantly changing globes.

Usually two of the globes blow in the first day or two of use, but the third globe will last much longer (at least a month, or until we replace the blown globes).

The globes we are using are Mirabella GU10 240V 50W (240V is standard for Australia).

I've heard about other people having this problem - I've searched the web and found plenty of discussions but no definitive answers.

What might be causing the problem and how can I fix it?

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Are you using halogens, and are you handling them correctly: i.e. not touching them directly, but holding them in a clean cloth when you're installing them. –  Niall C. May 30 '11 at 5:06
    
A picture of your situation would help. –  csmba May 30 '11 at 6:06
    
@csmba - thanks, have added pic. –  Greg Sansom May 30 '11 at 8:46
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@Niall C:Thanks for the insight - Yes they are halogens and I had no idea that they had to be handled without touching. Following your comment I did a bit of research and found that the grease left by fingers can burn, increasing the heat and causing the globe to blow. –  Greg Sansom May 30 '11 at 8:50
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If you were touching the bulbs, this is definitely the cause. Halogen bulbs are picky that way. (Also for cars in the headlights. It kills them quickly.) If not that, then the only other cause is probably voltage fluctuations. Is your power supply consistent? –  user558 May 30 '11 at 11:50

2 Answers 2

up vote 14 down vote accepted

If you're using halogen bulbs, you need to handle them correctly: don't touch them directly -- hold them in a clean cloth.

The reason is that halogens get much hotter than other bulbs. Oils from your fingerprints cause the bulbs to heat unevenly where you touch them, leading to thermal stresses which can crack the bulb.

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Holy crap, I had no idea halogens were that temperamental! That explains why I had one burn out in less than a month when I installed new track lighting last year. I wish I had done my research. –  Doresoom Jun 1 '11 at 17:28
    
I tried handling the globes correctly and they have now lasted over a week. I checked the packaging and the need for correct handling is not mentioned! Thanks :) –  Greg Sansom Jun 18 '11 at 9:42

Bottom line: switch to LED GU10 bulbs.

While there might be something wrong in the electrical wiring (I am no expert there), I would address the other option, which is that these halogen bulbs have a short life period since they are getting over-heated.

My suggestion would be simple: stop wasting money on inefficient halogen and switch to LED. For example: http://amzn.to/l4evos Even if you didn't have this problem that would be a good idea (LED would save you electricity), but given your problem, it is a double whammy. LED bulbs generate much much less heat then halogen, addressing the root of the problem.

Notice that a 3 or 4 W LED is not equivalent to 50W halogen. I would say that at best, 4W is equal to 35W (and even that is pushing it). So, you might be able to find a 5W LED, but if not, expect less light... but at least you will not be replacing bulbs every 4 weeks...

Is it 240V, meaning you are using a in-line, simple halogen bulbs (not low voltage halogen)? and is it 240v meaning you are not in the U.S?

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He mentions Australia in his question. –  user7116 Jun 1 '11 at 18:24
    
Compared to the halogen bulbs, the LED lights still produce a much worse quality of light: the CRI is 75 for the one linked, which is even worse than for compact fluorescent bulbs (CRI around 85). –  Lev Bishop Jun 2 '11 at 4:10
    
@Lev Bishop: I feel it's worth mentioning that LED lights can produce a better quality of light (even if the particular linked to bulbs do not). Many LED lights have a CRI over 90. –  qes Jun 9 '11 at 19:16

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