In ,
Adam Aglionby wrote:

On 16 Feb, 01:38, matthewb wrote:
On 14 Feb, 06:29, Mikeyboy wrote:

They are so on and off! I bought a ceiling light for my daughter's
bedroom with around 6 halogen (20w) in it. When you switch it on, you
are lucky if 4 of them come on. If you fiddle with the rest they
usually come on eventually, but once switched off, you are back to the
same scenario with at least two not working when you flick the switch.
In the bathroom I have 2 over the wash basin. One is fine, rock solid,
the other comes on if it feels like it.
Can anyone explain why this is to me?
is there an answer?
Sooooooo tedious. I think I'll go back to a single 150 w bulb till
they are impossible to find.

Consider not using Halogen all together. They have a short lifespan
and use too much energy. LED lights can work as a straight replacement
using 1/9 the power. Compact Fluorescent Lights exist the the same
size using 1/5 the power.
References:http://www.matthewb.id.au/index.php?...ticle&catid=6:
energy-effic...http://www.matthewb.id.au/media/Ligh...alculator.html

Added sci.engr.lighting as crosspost

Matthew creditable and nicely presented web site and calculator but
like your above figures , missing a vital piece of information, actual
useable light output.

"LED lights can work as a straight replacement using 1/9 the power."

Unfortunately not even close, LED is currently almost never a
`straight replacement` for halogen lamps, there getting better on an
almost weekly basis but having worked with LED sources for more than
10 years, they still are not a straight drop in replacement for a 50W
12V MR16 or even a GU10 MR16.

LEDs used in the right way , with an understanding of their advantages
and limitations are great and offer possibilities not possible with
any other light source.

What they don`t offer is a universal drop in replacement fo all other
forms of lighting, have to deal with people who have been oversold LED
lighting , at not inconsiderable expense, that dosen`t do what they
were sold on it would do.

Also, LEDs 9 times as efficient as halogen lamps sounds like a tall
claim to me. Halogen lamps used for lighting mostly achieve 15-21
lumens/watt. 9 times 15 is 135, and I have yet to hear of an LED on the
market that efficient, except for extreme of high end white ones when they
are seriously underpowered (like 50 mA for ones with 1 mm square ballpark
chips, rated 350-1500 mA). 80-100 lumens/watt sounds to me high side high
end for LED lighting products. Last time I checked out results of
D.O.E.'s "Caliper" program (November 2008 or so), high end was 60's
lumens/watt and few products got past the 40's.

"Compact Fluorescent Lights exist the the same size using 1/5 the power."

Most CFLs achieve close to 60 lumens/watt. Highest I have heard for one
consuming less than 45 watts (including ballast losses) is 70 lumens/watt
for Philips 25 watt "triple arch" SLS model.

Closer but again missing out quantity of light delivered on task,
original poster has problems with MR16, 50mm diameter, reflector
lamps. Compact fuorescent, some of them are actually compact cold
cathode which isnt as efficient as compact fluro, lamps in this style
have awful real world efficiency, the lamp is folded so much to fit in
the space that it obscures a large amount of its own output, they
really aren`t very good.

CFLs in reflectors also have wider beam spread and often lower
percentage of light within the beam than incandescent/halogen reflector
lamps have. The larger light source size makes the light harder to
control unless a similarly larger reflector/optic is used.

Lies, damned lies and statistics is still as true as it ever was.

Adam

I agree and maybe a little and-then-some!

CFLs and most white LEDs are more efficient than incandescents and
halogens, but exaggerated and/or excessively-optimistic claims of degree
of improvement appear to me to be common. Such excessively optimistic
and/or exaggerated claims lead to disappointment, and to skepticism and
distrust of new lightuing technologies, especially if marketed or
manufactured by anyone not having had a solid reputation in lighting for
at least something like a decade or two.

- Don Klipstein )