Halogen Downlights keep blowing (sometimes within 2 hours)

[Pat-UK]

Hi Guys,

Looking for some advice on an issue that's driving me mad.

This applies to one floor only, the other 3 floors blow them on a normal basis (one a month at worst)

The Kichen and utility floor (basment) has it's own CU there are 15 halogen downlights, on a 3 gang dimmer, rated at 400w per gang.

6 lamps on first gang, 5 on second gang and 4 on third.

I had issues with the electricians who rewired the place and had to have them back quite a few times before the trip would stop blowing down there also in a week the lighting destroyed 3 dimmer switches.

Anyhow to my issue, a lamp will last a maximum of 40 hours before it blows, sometimes they will blow within a few minutes.

It's got to the point that I only have 2 bulbs in each section as the cost of changing the whole set is crazy.

I have used Cheap and nasty, I have also used Expensive and have even tried some that have 10,000 hours on the side of the box. Makes no differance which ones I use, they still go POP !!!!!

Should I upset my electricians again and get them to check the wiring is OK or is it a Dimmer/Halogen known problem???

Many Thanks

 

[Spark123]

Mains or ELV? Is there space above the lamp for heat to escape? Are the lamp holders in good condition - any signs of pitting on the pins of the blown lamps? Are the lamps enclosed? Are you touching the quartz glass?

 

[ColJack]

halogens don't like being dimmed.. it's something to do with the way they work...

A halogen bulb is an ordinary incandescent bulb, with a few modifications. The fill gas includes traces of a halogen, often but not necessarily iodine. The purpose of this halogen is to return evaporated tungsten to the filament.
As tungsten evaporates from the filament, it usually condenses on the inner surface of the bulb. The halogen is chemically reactive, and combines with this tungsten deposit on the glass to produce tungsten halides, which evaporate fairly easily. When the tungsten halide reaches the filament, the intense heat of the filament causes the halide to break down, releasing tungsten back to the filament.
This process, known as the halogen cycle, extends the life of the filament somewhat.

Another problem with dimming of halogen lamps is the fact that the halogen cycle works best with the bulb and filament at or near specific optimum temperatures. If the bulb is dimmed, the halogen may fail to "clean" the inner surface of the bulb. Or, tungsten halide that results may fail to return tungsten to the filament. Halogen bulbs have sometimes been known to do strange and scary things when greatly dimmed.

it is not recomended to run halogens at less than 90% of it's rated power to maintain the halogen cycle..

you may get better results with an electronic dimmer because of the soft start many of them have..

why do you need to dim them?

I never understood that..

people have 30 x 50W halogens fitted, then put a dimmer on them because they are too bright...

just fit 20W lamps, or change the switching so you can turn them off in smaller banks to achieve the required lighting level..

I have rewired the 3 lamp light in my living room so that I can have 1, 2 or 3 lamps on depending on the "mood" i want..

EDIT: oh and since it's a basement with a kitchen and utility room, and you describe problems with tripping, then I'd sugest getting a damp survey done, it's very likely all the steam from the kitchen, utility and general damp from being a basement..