bulbs blowing

[Jim Walsh]

Hi. I recently had a kitchen fitted, the lighting of which included about 12 small 240V/ 50W halogen bulbs (the flat faced ones with two, mushroom shaped electrodes protruding from the base). Anyway, of these

12 bulbs, an average of 1 a week has blown since installation. Is this normal for this type of bulb and if not, what would be the possible cause(s) of premature failure? It's getting rather expensive at £10 a month just to keep all the lighting functioning. By the way, does anyone know why Wickes charge about twice the price for these bulbs compared to several other retailers e.g. Laver's ~£2.50; Screwfix ~£2.50; Wickes ~£5!!!

Regards, Jim.

[Christian McArdle]

Yes it is. However, they can often be improved if you can increase ventilation to the bulb holders.

I tend to avoid large numbers of filament lightbulbs at all times. They are a PITA. They might look nice, but they cost the earth, both in money and environmental damage.

Christian.

[Ben Edgington]

These sound the same as I put in to our kitchen. But I have only three (600W does seem quite a lot unless your kitchen is Big). None have blown in nearly 6 years. I run them off a dimmer, which perhaps helps, and contrary to other reports have had no blackening at all even when running dimmed for some time. They are quite well ventilated in the ceiling void above which also may make the difference.

Ben

[Christian McArdle]

Soft start makes little difference to lamp life in practice. Ventilation makes a big difference.

Christian.

[Peter Ashby]

We have a dimmer which you push for on/off and it still soft starts even on full. I can't remember the last time I changed that bulb. Can't remember the brand of the dimmer but it wasn't cheap, IIRC ?25-30.

Peter

[Christian McArdle]

The main method that dimmers improve bulb life is by them never reaching

100% brightness. A few percent off the top will extend bulb life quite noticeably.

Christian.

[parish]

Is it the type of dimmer where you turn the lights off by rotating the dimmer all the way down (rather than pushing the knob for on/off)? If so then switching them on is the reverse so you get a "soft start" which reduces the thermal shock to the lamp. I noticed when I was looking for LV halogens that many transformers feature soft start to (according to the blurb) increase lamp life.

[parish]

Does the bulb being open-fronted or glass-fronted have a significant impact on bulb life? I've ordered glass-fronted since they are for the kitchen and the existing bulbs seem to accumulate a fair amount of dirt and halogens run so hot (which is why of course you should never handle the bulbs with bare fingers when installing them as the grease can crack the envelope when they heat up).

[Dave Liquorice]

What does the packaging say about bulb life? 1000h? With 12 bulbs one could expect one to blow every 1000/12 hours or 83 hrs. How long are these light on per day? Divide that number of hours into 83 to see how often in days one could expect a bulb to blow. We are getting pretty close to your 1 a week...

Over voltage and over heating. Halogens run fing hot, they need good ventilation. On over voltage when we moved in here the 6 x 40W clear candle bulbs would go at about 1/week, slightly above the expected rate. Bought a UPS for the computers, I thought it was faulty as it immediatly switched into "voltage reduction" mode and stayed there. Started looging the voltage data from the UPS. The average was 250v peaking to 260, called the REC and they came, checked the voltage and adjusted the tapping on our transformer to the lowest available. We now have 237v average with maximums of about 245v. The clear candle bulbs now don't fail quite as fast, maybe 1 or 2 a month.

The market, charge what people will pay. Candle bulbs again. =A31.98 for=

2 in B&Q, =A32.45 (or maybe =A32.99) for 2 in Safeway. CEF =A34.71 for 1= 0...

[Andrew Gabriel]

Well, you have gone for dirt cheap fittings with a high running cost. That failure rate is correct for running them about 7 hours/day.

600W of lighting in most kitchens is completely ridiculas, and a good indicator of how ineffective such lighting is for that task.

[The Natural Philosopher]

No, they are superb, I have had just one blow, and that was none that came with a 'kit'' that had a bad connection and was flickering.

I got a shitload of bulbs from Newey and Eyre, they wer cheap, and they have all lasted over a year of continous usage pretty much.

[Bob Mannix]

What does the packaging say about bulb life? 1000h? With 12 bulbs one could expect one to blow every 1000/12 hours or 83 hrs.

Well one could, but one would be wrong! The distribution of bulb lives will be a normal distribution centred on 1000h and probably quite peaked and not, as you seem to think, a flat distribution between 0 and 1000h. The probabilty of a bulb with a nominal lifetime of 1000h failing in 83h (assuming no external faults) will be extremely small. 12 times this amount will still be extremely small.

[Ian Clowes]

Hi

We had one bulb that blew a couple of times. I popped the mount out of the ceiling and found that the wiring module was not clipped in properly. This had caused it to 'drift' towards the lamp, and (presumably) cause a hot spot that made the bulb fail. Once I reseated it the problem went away. So, check out behind the lamps and make sure there's plenty of space and everything is in place properly.

I think there are also two types of bulb, although this may be for different 'format' bulbs as used in display cases only. Some throw the heat forwards, others backwards. The latter are more comfortable to use, esp. if you have 8' ceilings when walking below them, but do rely on an amount of ventilation behind the bulb.

My other suggestion would be to get an electronic soft start dimmer from MK or some half decent make. They're not cheap at around £35 each for a two gang, and you need to make sure the circuit load is right for the dimmer. There are two 'standard' load ranges that I've seen. I think one is 75W-250W and the other is something like

100W-450W. You have to make sure the circuit load fits within the range. The MK one comes with a handy 'spacer' to build the face plate up if you need to mount it in a shallow back box.

HTH IanC

[Dave Liquorice]

Your assuming that all bulbs where put into service at the same instant. OK for a new installation they have been but it doesn't stay like that...

Over time there will be a fairly random selection of bulbs some just put into service, some partway through and others near the end of their lives.

[Bob Mannix]

This is true, but the OP was talking about a new installation AFAICR where the problem occurred immediately, so my answer was correct (if not complete!).