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tahir

Joined: 28 Oct 2004
Posts: 45670
Location: Essex

Posted: Thu Jun 16, 05 5:03 pm Post subject:
Get 'em in first, you never know you might find they're OK

jema
Downsizer Moderator

Joined: 28 Oct 2004
Posts: 28235
Location: escaped from Swindon

Posted: Thu Jun 16, 05 5:09 pm Post subject:

tahir wrote:

Get 'em in first, you never know you might find they're OK

You never know, and there is no great place/way for extra lights in the kitchen, so it will take a bit of thought anyway.,

jema
Downsizer Moderator

Joined: 28 Oct 2004
Posts: 28235
Location: escaped from Swindon

Posted: Fri Jun 17, 05 12:14 pm Post subject:

Quote:

Dear Martin
Thank you for your recent internet order. Unfortunately we are currently out of stock of this item and will no longer stock it. However, we will be stockng an alternative bulb which will appear on our webite next week.
I have therefore cancelled your order and wait to hear from you following the release of our new stock.
Regards
Hilary Ritchie
led-lightbulbs sales

tahir

Joined: 28 Oct 2004
Posts: 45670
Location: Essex

Posted: Fri Jun 17, 05 12:16 pm Post subject:
I'd say that's good news, I'd assume that the new version should improve on the old.

jema
Downsizer Moderator

Joined: 28 Oct 2004
Posts: 28235
Location: escaped from Swindon

Posted: Thu Jun 30, 05 5:30 pm Post subject:
Well I got them, and even with 7 bulbs in the kitchen, they don't really cut it

tahir

Joined: 28 Oct 2004
Posts: 45670
Location: Essex

Posted: Thu Jun 30, 05 5:31 pm Post subject:
Is that the new version?

jema
Downsizer Moderator

Joined: 28 Oct 2004
Posts: 28235
Location: escaped from Swindon

Posted: Thu Jun 30, 05 5:35 pm Post subject:
Yes, and I figure they need at least twice the output to get to a sensible level. I will probably swap out a couple for "real" bulbs.

tawny owl

Joined: 29 Apr 2005
Posts: 563
Location: Hampshire

Posted: Fri Jul 01, 05 8:40 am Post subject:

On the subject of bulbs generally, does anyone know whether halogens are as/more green than energy-saving ones? I've tried the energy-saving ones (several types) and I find they all give a pathetic and rather eye-straining light, and also seem to blow a lot faster than normal bulbs. Most of our fittings are halogen anyway, and I'm considering changing some of the others. I'm assuming halogens aren't too bad, considering they are generally only 25 or 50 watt, but I'd be interested to know for sure.

jema
Downsizer Moderator

Joined: 28 Oct 2004
Posts: 28235
Location: escaped from Swindon

Posted: Fri Jul 01, 05 8:56 am Post subject:

tawny owl wrote:

240v Halogens are horrible. expensive and blow all the time.

Northern_Lad

Joined: 13 Dec 2004
Posts: 14210
Location: Somewhere

Posted: Fri Jul 01, 05 9:02 am Post subject:

jema wrote:

240v Halogens are horrible. expensive and blow all the time.

Odd, I've had 5 in my kitchen for nearly 2 years now without a problem. I'd prefer to use 12V, but I've got them on a dimmer switch so I don't blind myself on dark mornings.

jema
Downsizer Moderator

Joined: 28 Oct 2004
Posts: 28235
Location: escaped from Swindon

Posted: Fri Jul 01, 05 9:14 am Post subject:

Northern_Lad wrote:

jema wrote:

240v Halogens are horrible. expensive and blow all the time.

Odd, I've had 5 in my kitchen for nearly 2 years now without a problem. I'd prefer to use 12V, but I've got them on a dimmer switch so I don't blind myself on dark mornings.

Well I have tried various brands and none of them live up to hours of life promised, and my brother says the same thing. It might be something to do with electric supply quality, but whatever it is I got sick of buying them.

Lloyd

Joined: 24 Jan 2005
Posts: 2699

Posted: Fri Jul 01, 05 9:16 am Post subject:
I have used 50w 12v Osram halogen spots in office and kitchen for a couple of years, but as Jema says, they keep blowing, and are expensive to replace. Better, however, than the long life ones, that keep you in semi darkness.

tawny owl

Joined: 29 Apr 2005
Posts: 563
Location: Hampshire

Posted: Sun Jul 03, 05 6:12 pm Post subject:

Northern_Lad wrote:

Odd, I've had 5 in my kitchen for nearly 2 years now without a problem. I'd prefer to use 12V, but I've got them on a dimmer switch so I don't blind myself on dark mornings.

Me too - they do blow now and again, but I certainly wouldn't say more often than normal bulbs. Mine's on dimmer as well - maybe it's the sudden surge of leccy that blows them?

jema
Downsizer Moderator

Joined: 28 Oct 2004
Posts: 28235
Location: escaped from Swindon

Posted: Sun Jul 03, 05 7:03 pm Post subject:

Quote:

Halogen Bulb Failure Modes
Halogen bulbs usually fail the same way that ordinary incandescent bulbs do, usually from melting or breakage of a thin spot in an aging filament.
Thin spots can develop in the filaments of halogen bulbs, since the filaments can evaporate unevenly and the halogen cycle does not redeposit evaporated tungsten in a perfect, even manner nor always in the parts of the filament that have evaporated the most.
However, there are additional failure modes.
One failure mode is filament notching or necking. Since the ends of the filament are somewhat cool where the filament is attached to the lead wires, the halogen attacks the filament at these points. The thin spots get hotter, which stops the erosion at these points. However, parts of the filament even closer to the endpoints remain cool and suffer continued erosion. This is not so bad during continuous operation, since the thin spots do not overheat. If this process continues long enough, the thin spots can become weak enough to break from the weight of the filament.
One major problem with the "necked" ends of the filament is the fact that they heat up more rapidly than the rest of the filament when the bulb is turned on. The "necks" can overheat and melt or break during the current surge that occurs when the bulb is turned on. Using a "soft-start" device prevents overheating of the "necks", improving the bulb's ability to survive "necking". Soft-start devices will not greatly extend the life of any halogen bulbs that fail due to more normal filament "thin spots" that run excessively hot.
Some halogen bulbs may usually burn out due to filament end necking, and some others may usually burn out from thin, hot spots forming in the filament due to uneven filament evaporation/recovery. Therefore, some models may have a significantly extended life from "soft-starting" and some other models may not.
It is generally not a good idea to touch halogen bulbs, especially the more compact, hotter-running quartz ones. Organic matter and salts are not good for hot quartz. Organic matter such as grease can carbonize, leaving a dark spot that absorbs radiation from the filament and becomes excessively hot. Salts and alkaline materials (such as ash) can sometimes "leach" into hot quartz, which typically weakens the quartz, since alkali and alkaline earth metal ions are slightly mobile in hot glasses and hot quartz. Contaminants may also cause hot quartz to crystalize, weakening it. Any of these mechanisms can cause the bulb to crack or even violently shatter. If a quartz halogen bulb is touched, it should be cleaned with alcohol to remove any traces of grease. Traces of salt will also be removed if the alcohol has some water in it.
Since the hotter-running quartz halogen bulbs could possibly violently shatter, they should only be operated in suitable fully enclosed fixtures.

Use of Halogen Bulbs with Dimmers
Dimming a halogen bulb, like dimming any other incandescent lamp, greatly slows down the formation of thin spots in the filament due to uneven filament evaporation. However, "necking" or "notching" of the ends of the filament remains a problem. If you dim halogen lamps, you may need "soft-start" devices in order to achieve a major increase in bulb life.
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.
Halogen bulbs should work normally at voltages as low as 90 percent of what they were designed for. If the bulb is in an enclosure that conserves heat and a "soft-start" device is used, it will probably work well at even lower voltages, such as 80 percent or possibly 70 percent of its rated voltage. However, do not expect a major life extension unless soft-starting is used. Even with soft-starting, do not expect to more than double or possibly triple the life of any halogen bulb already rated to last 2,000 hours or more. Even with soft starting, the life of these bulbs will probably not continue to improve much as voltage is reduced to less than about 90 percent of the bulb's voltage rating.

Dimmers can be used as soft-start devices to extend the life of any particular halogen bulbs that usually fail from "necking" of the ends of the filament. The bulb can be warmed up over a period of a couple of seconds to avoid overheating of the "necked" parts of the filament due to the current surge that occurs if full voltage is applied to a cold filament. Once the bulb survives starting, it is operated at full power or whatever power level optimizes the halogen cycle (usually near full power)
The dimmer may be both "soft-starting" the bulb and operating it at slightly reduced power, a combination that often improves the life of halogen bulbs. Many dimmers cause some reduction in power to the bulb even when they are set to maximum.
(A suggestion from someone who starts expensive medical lamps by turning up a dimmer and reports major success in extending the life of expensive special bulbs from doing this.)

Interesting stuff from:

https://members.misty.com/don/bulb1.html#hb

tawny owl

Joined: 29 Apr 2005
Posts: 563
Location: Hampshire

Posted: Sun Jul 03, 05 8:16 pm Post subject:
So that's basically 'yes', then? Thanks, Tahir - very informative, even if some of it was over my head!

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