TOT halogen efficiency

nospam wrote:

"Bill Wright" wrote:

Can anyone cast any light (geddit?) on this? Are 12V lamps really so much
more efficient? If so, why?

Because the 20 times lower resistance means the filaments are 20 times
more substantial and can be run at a higher (and so more efficient)
temperature without mechanically falling to bits or evaporating away
unreasonably quickly.

Filament lamps have always been a trade off between efficiency and life
with deposition of evaporated filament on the glass enclosure being a
consideration which higher enclosure temperature and halogen gas content
mitigates.

--

Er. It's actually 400 times lower resistance. The 12V bulb draws 20 times
more current for the same wattage at 1/20th the voltage.

No wonder the 240V ones are disappointing.

--
Steve Hayes, South Wales, UK
----Remove colours from reply address----

"Bill Wright" wrote in message
...
Some time ago I reported in this hallowed forum my disapointment at the
apparent inefficiency of some mains voltage halogen downlights I'd fitted
in the dining room. Based on the 12V halogens I have used elsewhere I
expected the room would need eight 25 watt lamps. In fact it needed eight
50W ones. 400W to light a medium sized room!

In our kitchen we have a twin 8 foot fluorescent fitting. 200W, but about
five times the light output of your halogens - nice and even too. You can
get different colour temperature tubes (we use 3k5 to 4kK). The last around
a decade and cost under a fiver.

Halogen puts out a lot of heat too.

Look at LED lighting. Already twice as efficient as CFL, 50kh MTBF and soon
there will be new forms which will give much better light than any
incandescent arrangement.


I'm now intending to put new lights in the kitchen. Today I lit a 12V 20W
lamp and a 240V 25W lamp side by side. Both lamps were the 36deg type.
The 12V lamp was much brighter. I was running it on 12.00VDC, but the
current drawn was 1.7A which equates to 20.4W, so I guess the brightness
would be the same on a nominal 12V AC supply. The 12V lamp had a neutral
colour, whereas the mains lamp was rather warm. I wonder if this accounts
for the greater efficiency of the 12V lamp, and means that the mains lamp,
being relatively under-run, will last longer.

I reduced the voltage on the 12V lamp until it had the same apparent
brightness as the mains lamp. At 8.7V both lamps had the same brightness
and colour temperature, as near as I could tell.

Can anyone cast any light (geddit?) on this? Are 12V lamps really so much
more efficient? If so, why?

You can run them hotter for longer.


Bill

R. Mark Clayton wrote:
"Bill Wright" wrote in message
...
Some time ago I reported in this hallowed forum my disapointment at the
apparent inefficiency of some mains voltage halogen downlights I'd fitted
in the dining room. Based on the 12V halogens I have used elsewhere I
expected the room would need eight 25 watt lamps. In fact it needed eight
50W ones. 400W to light a medium sized room!

In our kitchen we have a twin 8 foot fluorescent fitting. 200W, but about
five times the light output of your halogens - nice and even too. You can
get different colour temperature tubes (we use 3k5 to 4kK). The last around
a decade and cost under a fiver.

Halogen puts out a lot of heat too.

Look at LED lighting. Already twice as efficient as CFL, 50kh MTBF and soon
there will be new forms which will give much better light than any
incandescent arrangement.

I'm now intending to put new lights in the kitchen. Today I lit a 12V 20W
lamp and a 240V 25W lamp side by side. Both lamps were the 36deg type.
The 12V lamp was much brighter. I was running it on 12.00VDC, but the
current drawn was 1.7A which equates to 20.4W, so I guess the brightness
would be the same on a nominal 12V AC supply. The 12V lamp had a neutral
colour, whereas the mains lamp was rather warm. I wonder if this accounts
for the greater efficiency of the 12V lamp, and means that the mains lamp,
being relatively under-run, will last longer.

I reduced the voltage on the 12V lamp until it had the same apparent
brightness as the mains lamp. At 8.7V both lamps had the same brightness
and colour temperature, as near as I could tell.

Can anyone cast any light (geddit?) on this? Are 12V lamps really so much
more efficient? If so, why?

You can run them hotter for longer.

Bill




Quite interesting OT thread..

I had 4x 12V 35w downlighters in my new kitchen (maybe 10 years ago),
nice curvy chome job from B&Q, but the bulb connectors didn't last.
Basically burnt after about 2 years and not functional. I replaced a
few with Maplin connectors and seemed to be ok once I got a high temp
connector block.

In Engineering mode and increased talk of climate change etc, I tried to
reduce the operation temp by using LEDs, even spent £20 on one 3w unit
that was very directional but still not half the light from the halogen.
Eventually I replaced it with a 3 way, Philips pinned fluorescent in
fogged glass. Much whiter than the soft typical filament replacement bulbs.

The ones in the bathroom are 50W mains units and have lasted 6 years,
but I guess don't get left on as much.

If there are decent LEDs out there I havn't been able to buy them, but I
appreciate the technology is improving rapidly, but most at the expense
of ..well expense.

Surprisingly the number of decent looking fluorescent fittings, other
than your basic strip/tube is very limited. I'm quite happy to live
with the less warm light from fluorescents in order to save power, I
even look for the long life time ones, but it has to pass muster with
the other half.

--
Tony

On 5 July, 23:49, John Rumm wrote:
Adam Aglionby wrote:
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]
Again , your suggestions for currently availabke suitable replacement
lighting?
Your source for beleiving MR16 will be "outlawed" within 5 years?
I did not see Andy make reference to MR16 in particular. However the
general EU timetable is described at the end of this document:

http://ec.europa.eu/energy/efficiency/ecodesign/doc/committee/2008_12....

I took the inference that he was refering to MR16 both LV and GU10
being ill advised for a new installation because of an uncertain
future.

I expect his ire was more focussed on GU10 in particular than the
overall form factor. However I stand to be corrected.

Problem is people read it as all MR16 format lighting including LV.


The timetable relies on suitable alternatives being developed , for a
lot of uses of MR16 lamps there is no current or on the horizon
replacement.

Well the difficulty is who gets to decide what is "suitable". Many would
argue that there is currently no suitable replacement for a 100W GLS
bulb - the alternatives having poorer colour rendition and/or slow warm
up times, or incompatibility with dimmers, plus a range of other
problems. However this does not seem to have stopped the powers that be
from suggesting that these can be replaced with CFL substitutes.

More than suggesting :-(

Ingo Maurer, lighting designer who came up with LV MR16 lights on
wires amongst other things, protests ;-)

http://www.designboom.com/weblog/cat/8/view/6169/ingo-maurer-euro-condom.html

Cheers
Adam





--
Cheers,

John.

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"Tony" wrote in message
...
R. Mark Clayton wrote:
"Bill Wright" wrote in message
...
Some time ago I reported in this hallowed forum my disapointment at the
apparent inefficiency of some mains voltage halogen downlights I'd
fitted
in the dining room. Based on the 12V halogens I have used elsewhere I
expected the room would need eight 25 watt lamps. In fact it needed
eight
50W ones. 400W to light a medium sized room!

SNIP


Quite interesting OT thread..

I had 4x 12V 35w downlighters in my new kitchen (maybe 10 years ago),
nice curvy chome job from B&Q, but the bulb connectors didn't last.
Basically burnt after about 2 years and not functional. I replaced a
few with Maplin connectors and seemed to be ok once I got a high temp
connector block.

In Engineering mode and increased talk of climate change etc, I tried to
reduce the operation temp by using LEDs, even spent £20 on one 3w unit
that was very directional but still not half the light from the halogen.
Eventually I replaced it with a 3 way, Philips pinned fluorescent in
fogged glass. Much whiter than the soft typical filament replacement
bulbs.

The ones in the bathroom are 50W mains units and have lasted 6 years,
but I guess don't get left on as much.

If there are decent LEDs out there I havn't been able to buy them, but I
appreciate the technology is improving rapidly, but most at the expense
of ..well expense.

Prices of LED lights are falling and spec's are rising.

We have a 1.4W R50 spot light, that has decent output and was fairly cheap.

MTBF and consumption relative to GLS for lighting is roughly

GLS 1,000 hours 100%
Tungsten 2,000 hours 50%
CFL 10,000 hours 20%
LED 50,000 hours. 10%



Surprisingly the number of decent looking fluorescent fittings, other
than your basic strip/tube is very limited. I'm quite happy to live
with the less warm light from fluorescents in order to save power, I
even look for the long life time ones, but it has to pass muster with
the other half.

--
Tony