Hi
Just had a look at some 240V halogen downlighters from B&Q.
I have noticed that the bulb or rather the reflector part of it has
diffrent color to LV 12V ones /240V clear , 12V slight colour shading/
Is there any noticable diffrence between them in terms of the light output
per Watt.
and the light quality itself?

Rafal

In article ,
"Rafal" writes:
Hi
Just had a look at some 240V halogen downlighters from B&Q.
I have noticed that the bulb or rather the reflector part of it has
diffrent color to LV 12V ones /240V clear , 12V slight colour shading/
Is there any noticable diffrence between them in terms of the light output
per Watt.
and the light quality itself?

Both types are available in aluminium or dichroic reflectors.
(Actually, aluminium LV lamps have become difficult to find.)
Dichroic reflectors don't reflect the heat so the beam is
cooler, but the fitting has to be able to handle the extra
heat dumped backwards into it.

The type of reflector makes negligable difference to the light
output per watt, but the voltage difference certainly does.
The 12V lamps are significantly more efficient than 240V ones.
Also, because 12V lamps can be built with much smaller filaments,
it is possible to control the light distribution much more
accurately than with 240V ones, and you'll find a wider range of
beam angles available, with the optics also able to better
control light spill outside the intended beam.

--
Andrew Gabriel

There is always the problem with LV ones of the transformer going... usually
it's been tucked into the most ackward of places too.

For tons of data on the different LV and Mains Voltage lamps available then
check he
http://www.tlc-direct.co.uk/Technica...a/LampData.htm

"Andrew Gabriel" wrote in message
...
In article ,
"Rafal" writes:
Hi
Just had a look at some 240V halogen downlighters from B&Q.
I have noticed that the bulb or rather the reflector part of it has
diffrent color to LV 12V ones /240V clear , 12V slight colour shading/
Is there any noticable diffrence between them in terms of the light
output
per Watt.
and the light quality itself?

Both types are available in aluminium or dichroic reflectors.
(Actually, aluminium LV lamps have become difficult to find.)
Dichroic reflectors don't reflect the heat so the beam is
cooler, but the fitting has to be able to handle the extra
heat dumped backwards into it.

The type of reflector makes negligable difference to the light
output per watt, but the voltage difference certainly does.
The 12V lamps are significantly more efficient than 240V ones.
Also, because 12V lamps can be built with much smaller filaments,
it is possible to control the light distribution much more
accurately than with 240V ones, and you'll find a wider range of
beam angles available, with the optics also able to better
control light spill outside the intended beam.

--
Andrew Gabriel

Rafal wrote:

Just had a look at some 240V halogen downlighters from B&Q.
I have noticed that the bulb or rather the reflector part of it has
diffrent color to LV 12V ones /240V clear , 12V slight colour shading/

You may have been comparing a bulb with an standard aluminium reflector
against one with a dichroic reflector. On the latter type, the reflector
reflective to most of the visible spectrum, but translucent for some
parts of it and also for most of the infra-red wavelengths. The
advantage is they do not project as much heat forward as the standard
aluminium reflector ones. The also tend to look slightly nicer for
display lighting as the slight colour staining you get from different
angles can look quite attractive.

(you should not use dichroic bulbs unless the fitting is designed for
them, because the fitting will get hotter)

Is there any noticable diffrence between them in terms of the light output
per Watt.
and the light quality itself?

The LV ones will give more light per watt. They also have a thicker
filament and hence are more tolerant of vibration and shock.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

John Rumm wrote in message news:pPmac.

The LV ones will give more light per watt. They also have a thicker
filament and hence are more tolerant of vibration and shock.

And LV bulbs are a fraction the price of 240v ones. LV has all the advantages.

Regards, NT

N. Thornton wrote:

John Rumm wrote in message news:pPmac.


The LV ones will give more light per watt. They also have a thicker
filament and hence are more tolerant of vibration and shock.


And LV bulbs are a fraction the price of 240v ones. LV has all the advantages.


Apart from ease and cheapness of installation.



Regards, NT

Thank you all for excellent fedback.
Just what I needed
12V rules

Rafal

John Rumm wrote
Rafal wrote:

Just had a look at some 240V halogen downlighters from B&Q.
I have noticed that the bulb or rather the reflector part of it has
diffrent color to LV 12V ones /240V clear , 12V slight colour shading/

You may have been comparing a bulb with an standard aluminium reflector
against one with a dichroic reflector. On the latter type, the reflector
reflective to most of the visible spectrum, but translucent for some
parts of it and also for most of the infra-red wavelengths. The
advantage is they do not project as much heat forward as the standard
aluminium reflector ones. The also tend to look slightly nicer for
display lighting as the slight colour staining you get from different
angles can look quite attractive.

Hmm, that's all well and good but how does the light look in real
terms. I have LV and 240 halogens installed, the LV is clear white,
the 240V have a yellow tinge and don't appear to throw out much light.

What is this dichroic of which you speak. are these whiter ?

Cheers,

Paul.

Zymurgy wrote:

Hmm, that's all well and good but how does the light look in real
terms. I have LV and 240 halogens installed, the LV is clear white,
the 240V have a yellow tinge and don't appear to throw out much light.

I think you are right - you get more light for a given wattage from the
LV. Also you may find that with modern LV transformers (i.e. ones which
are not transformers at all, but actually small switched mode power
supplies) they will be less affected by local voltage sags and brownouts
that can give the 240V cousins a yellow tinge.

What is this dichroic of which you speak. are these whiter ?

You can get dichroic bulbs in LV and 240V although they are more common
in LV. It just describes the way in which the reflector is designed. A
standard bulb will normally have a metal (aluminium) coated reflector
that reflects like a mirror - most of the frequencies of light (and
hence infra red/heat) produced by the hot filament get projected
forward. As a result you are stuck with the natural output spectrum of a
discharge lamp - which is not very daylight like - giving the yellower
light plus lots of heat.

The dichroic (literally "having two colours" or "two frequencies")
reflectors allow some "colours" to pass through the reflector while
reflecting others. This lets you "tune" or equalise the colour of the
projected light and at the same time loose some of the projected heat
(it is still generated but more is absorbed by the light fitting).
Hence you get a different quality of light from them - making them seem
more natural and whiter. They also tend to make for slightly more
"specular" illumination. Hence shiny things seem more reflective and
sparkly, which is why they are good for shop displays and spot
highlighting in buildings.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

John Rumm wrote in message .. .
Zymurgy wrote:

Hmm, that's all well and good but how does the light look in real
terms. I have LV and 240 halogens installed, the LV is clear white,
the 240V have a yellow tinge and don't appear to throw out much light.

I think you are right - you get more light for a given wattage from the
LV. Also you may find that with modern LV transformers (i.e. ones which
are not transformers at all, but actually small switched mode power
supplies) they will be less affected by local voltage sags and brownouts
that can give the 240V cousins a yellow tinge.

What is this dichroic of which you speak. are these whiter ?

You can get dichroic bulbs in LV and 240V although they are more common
in LV. It just describes the way in which the reflector is designed. A
standard bulb will normally have a metal (aluminium) coated reflector
that reflects like a mirror - most of the frequencies of light (and
hence infra red/heat) produced by the hot filament get projected
forward. As a result you are stuck with the natural output spectrum of a
discharge lamp - which is not very daylight like - giving the yellower
light plus lots of heat.

The dichroic (literally "having two colours" or "two frequencies")
reflectors allow some "colours" to pass through the reflector while
reflecting others. This lets you "tune" or equalise the colour of the
projected light and at the same time loose some of the projected heat
(it is still generated but more is absorbed by the light fitting).
Hence you get a different quality of light from them - making them seem
more natural and whiter. They also tend to make for slightly more
"specular" illumination. Hence shiny things seem more reflective and
sparkly, which is why they are good for shop displays and spot
highlighting in buildings.

Excellent, thanks. Exactly what I wanted to know.

This ...

you are stuck with the natural output spectrum of a discharge lamp - which is not very daylight like - giving the yellower light plus lots of heat.

Is exactly what I have.

I'll try new bulbs, otherwise the fitting is coming down. Even with
200W kicking out in the kitchen it's still dull in there.

Cheers,

Paul.

What size is your kitchen? My is 3.40m X 2.40m, 2.70m high
and I planned for 4 x 50W 12V lights.
Looks like it may not be enough