How many Downlights and a few other related questions?

[kendor]

Is that the mains version? great bargain by the sounds of it if they are.

 

[kendor]

salem 2000 wrote:

What do you guys think about the life span of Halogen lamps, I've seen cheap ones pop after an hour.

Tungsten Halogen lamps by nature will have a shorter lifespan than their ordinary tungsten counterparts as they are designed to run much hotter to produce more light output, the halogen and rare gases inside help the filament last a bit longer by the process of re-depositing back onto the filament, molecules that escape from the filament because of the high temperatures involved and also help keep the glass envelope from "fogging" up too quickly on the inside.

In the lighting industry it is not good practise to run or start Halogen lamps at full voltage, usually 70% is the norm for the correct colour temperature of the lamp control being achieved with dimmers, another method of prolonging life of lamps used is Preheating and most if not all professional good quality dimmers have this facility, which as the name suggests is a method of keeping the filament warm so as not to shock stress it as you would starting from cold apart from it's other purpose in making the lamp more responsive to fading up in a hurry.

 

[ban-all-sheds]

Any thoughts on the information provided here which seems to suggest that permanently running halogens at less than full voltage will shorten their life. Or does that only apply to ELV ones?

 

[ban-all-sheds]

What do you guys think about the life span of Halogen lamps, I've seen cheap ones pop after an hour.

As BR said, buying 240V rated good brand lamps helps. The quality brand issue is fairly obvious, but do also watch for 240V and not 230V lamps. Without wishing to go through all the explanatory rigmarole again, our supply is still 240V in practice, and that 4% over-voltage can halve the life of a lamp.

And if you are sceptical, see here and ask yourself why Philips would make both 230V and 240V versions of their mains halogens if it didn't matter...

 

[kendor]

Any thoughts on the information provided here which seems to suggest that permanently running halogens at less than full voltage will shorten their life. Or does that only apply to ELV ones?

Interesting remarks made but i would like to see where the original information came from before making comment on it, it states that the information came from the Philips lighting forum this may have been a posting from someone rather than an official reply?


We do have ELV lamps supplied through dimmable transformers at work that are fed by dimmers these are used constantly usually at 50-60% operational level and seem to be the most reliable of all the lamps we use.

I think most of the above postings talking about lifespan though were to do with the mains voltage types.

 

[JDLDIY]

I bought and installed some mains voltage halogen downlighters recently. They are really cool, very well made and I would recommend them without hesitation. They are made by Eglo. They needed 70mm clearance for heat dissipation, both above the fitting and all around. I've heard of people using chicken wire mesh to hold back insulation for this.
JD

P S I run mine off a 2 way switch circuit, using about 3 junction boxes to make the wiring all neat and tidy. Be careful to buy dimmers with the right capacity, I bought mine from the same shop as the lights and they had to special order it. They admitted that they had been advising people wrongly until recently - for 5 x 50W lights I needed a 600W dimmer from memory. I didn't check the maths as such (knowing that if wrong we were being over safe), but worth looking into.

JD

 

[kendor]

jdldiy wrote:
P S I run mine off a 2 way switch circuit, using about 3 junction boxes to make the wiring all neat and tidy. Be careful to buy dimmers with the right capacity, I bought mine from the same shop as the lights and they had to special order it. They admitted that they had been advising people wrongly until recently - for 5 x 50W lights I needed a 600W dimmer from memory. I didn't check the maths as such (knowing that if wrong we were being over safe), but worth looking into.

JD

Nothing wrong with getting a larger capacity than needed dimmer it allows for expansion in the future.

 

[JDLDIY]

Nothing wrong with getting a larger capacity than needed dimmer it allows for expansion in the future

Absolutely agree. I just mention it for what it's worth, someone with more expertise than me may be able to throw more light on it. From what I can recall the shop said that the minimum I required was a 500W dimmer, twice the total wattage of the downlights.

JD

 

[kendor]

i'm not so sure about this "twice the rated load" for the dimmer advice, when the dimmer quotes a max wattage then it is designed to cope adequately with a load up to that rating, there would be a slight underating in fact, although that doesn't allow one to overload it.

 

[securespark]

Dimmers should be derated when used for mains voltage t/h. Full load cannot be applied without damage to the dimmer.

 

[il78]

Is that the mains version? great bargain by the sounds of it if they are.

yeah, I hunted around the wholesellers and all wanted around 1.50 each and I aint paying Q&B prices, a fiver for 2.....

Ever heard of www.stearn.co.uk dont think they are open to the public..........

 

[securespark]

il mate, stearns don't even serve traders, or if they do, they need shooting.

They only supply the wholesalers (all apart from WF, who they've fallen out with, cos stearns is now part of edmondson.