Halogen >> Downlighters >> Transformer

Rotara · 22 Apr 2005

Hi guys,
I'm looking to transform my home into something chic & space agey.
One way of getting the desired ambience is to install clever little spots in each room controlable with remote dimmers..

Questions are:

1. How many spots do you think i'll need for a room measuring 13.5' x 13.5'?
(giving even coverage under full intensity)

2. Should I go tranformer route or direct (240v) wired? (why?)

3. Is it safe (not withstanding adequate connection & insulation) to acquire the feed from the ceiling rose?

4. What type of spots should I go for & if recommending transformer route should I get one transformer that feeds all the spots or let each have their own? (why?)

Cheers
Ro.

plugwash · 22 Apr 2005

well i've anwered a few of your questions other people can probablly fill in on other things

Rotara said:
2. Should I go tranformer route or direct (240v) wired? (why?)

low voltage halogens are slightly brighter for a given power and some prefer the color of thier light BUT you have the hassle of fitting and possiblly replacing the transformers

Rotara said:
3. Is it safe (not withstanding adequate connection & insulation) to acquire the feed from the ceiling rose?

the main thing to watch is total load on the lighting cuircuit you don't want to have more than about 1000W total on a normal lighting cuircuit.

as for actual connection you would normally replace the rose with a junction box or similar.

Rotara said:
4. What type of spots should I go for & if recommending transformer route should I get one transformer that feeds all the spots or let each have their own? (why?)

having one transformer is a single point of failure which you may not like. Also single light transformers are often small enough that you can get them out for replacement by removing the downlighter (usefull downstairs when you don't want to have to take up the floor above. Also make sure you buy good quality transformers from a decent lighting supplier or electrical wholesaler. The ones the diy sheds sell seem to die very quickly.

ban-all-sheds · 22 Apr 2005

Rotara said:
1. How many spots do you think i'll need for a room measuring 13.5' x 13.5'?
(giving even coverage under full intensity)

Good question. If ever you get a good answer, or find some design software, let us know

2. Should I go tranformer route or direct (240v) wired? (why?)

Opinion is divided. LV (i.e. mains voltage) are easier to dim, easier to wire (much lower current), cheaper to buy and are where the developments in LED lamps are taking place. ELV (i.e. 12V) produce a crisper light, and more of it for a given wattage.

All other things being equal I personally would go for LV, but others will advise ELV. It'll have to be a personal choice. The only thing I would say is don't be misled by the apparent cheapness of ELV products in the sheds - the "transformers" are almost always rubbish and fail with dismaying regularity. Replacing them with decent ones, or buying quality products from a proper lighting supplier is to be advised if you go down the 12V road...

3. Is it safe (not withstanding adequate connection & insulation) to acquire the feed from the ceiling rose?

Should be - if you think about it the terminals in the first rose on a lighting circuit could be asked to carry the rated load of that circuit. Do note though that whether LV or ELV, spots and downlighters produce much less light than the equivalent GLS pendant, and a room which was perfectly OK with 2 x 100W pendants might need 5 x that with other types. So never mind the ceiling rose, watch your total load, as the lighting circuit will almost certainly be limited to 1300-1400W.

4. What type of spots should I go for & if recommending transformer route should I get one transformer that feeds all the spots or let each have their own? (why?)

Usual recommendation is 1 tx per luminaire (for reasons of reliability, I believe).

ban-all-sheds · 22 Apr 2005

I must learn to type faster..

keyplayer · 22 Apr 2005

Rotara said:
Hi guys,
I'm looking to transform my home into something chic & space agey.

You need a couple of lava lamps.

breezer · 22 Apr 2005

Rotara said:
1. How many spots do you think i'll need for a room measuring 13.5' x 13.5'?
(giving even coverage under full intensity)

that depends on the lux level intenscity you want (how bright)
"problem" is that the lamps usually create a cone shape of light (depending on fitting, and you did say spot lights) so if you have all "normal" ceiling lights you will actually make a room that is lit with a load of cones, this is great if they are coloured and you put them near a wall. (if that is what you like)

some will say have a "perimiter" of lights, but what about the middle? and how far apart should you have them?

as for having a dimmer why that will only dim all the lights, why not split the room into 2 or 3 regarding lighting, say have 2 dimmers controlling alternate lights?

I think lighting is grossly under rated, but as far as i know there is no cheaap programme for working out how many lights to light a room. at the end of the day it is going to be up to you

Rotara · 22 Apr 2005

Thanks guys,

I now see that going the 240v route is slightly less hassle & more reliable than using transformers.
But,,
Just for a little more comparison between the 2 systems before I decide..:

If I had say 8 lights mounted in the ceiling using the direct voltage route (240v).. Would they:::

a. Use more energy (i.e. cost me more money to run)?
b. Have more of a loading on the lighting circuit than a transformer lighting the same number of lights (8)?

(reason why is because i'm planning to kit out the whole house in these lights.. as well as look nice I thought using 12v transformers would save energy?)

HDRW · 22 Apr 2005

Rotara said:
Hi guys,
I'm looking to transform my home into something chic & space agey.

Hey, this it the Electrics forum - we don't do that!

Rotara said:
If I had say 8 lights mounted in the ceiling using the direct voltage route (240v).. Would they:::

a. Use more energy (i.e. cost me more money to run)?
b. Have more of a loading on the lighting circuit than a transformer lighting the same number of lights

(reason why is because i'm planning to kit out the whole house in these lights.. as well as look nice I thought using 12v transformers would save energy?)

Well if you're looking to save energy, getting the sort of lights you're talking about is the wrong way anyway - just think, 8 x 20W downlights (the least powerful type) is 160W, or about the same as three five-foot flourescent tubes. The latter would look like a brightly-lit shop if you had them in an average room, the former would look like a dimly-lit cave!

I'm afraid that chic and energy saving don't really go together in this case, basically because directional lights look nice, but omnidirectional lights are most efficient. And incandescent lights (of any voltage) give out more heat than light, which is how modern energy-saving (fluorescent) lamps work - less heat, more light for your money.

Sorry!

Howard

HDRW · 22 Apr 2005

breezer said:
I think lighting is grossly under rated

Hey, you speak for yourself - it's properly-rated at 6A in my house!

Cheers,

Howard

Rotara · 22 Apr 2005

cheers Howard,

makes sense now!

But does 8 directly (240v) wired halogens burn more energy than 8 12v ones?

Cheers.

ban-all-sheds · 22 Apr 2005

8 x 50W mains halogens will consume 400W

8 x 50W 12V halogens will consume slightly more because of losses in the transformers.

felix · 22 Apr 2005

Here's something you might want to think about. Halogen lamps don't take well to being dimmed. As in a standard filament bulb, tungsten vapour boils off the filament and deposits itself on the envelope. (This actually happens faster in a halogen bulb because it runs at higher temperature.) The purpose of the halogen is to combine with this tungsten and carry it back as a vapour. To make this work the envelope must be b****y hot! Now for the clever bit. At the white hot filament the tungsten halide breaks down and puts the tungsten back where it came from. Neat huh!

The problem with dimming one is that the envelope ceases to be so b****y hot and so the tungsten recycling system can't work.

You get more visible light per watt from halogen bulbs than from standard filaments because of the higher running temperature. (It's a sobering thought that very little of your input power generates light in the visible part of the spectrum.) Unfortunately the claims about needing more watts for your room are also true. You get a very bright cone of light from a halogen spot but the overall illumination is lower than that from a nice round bulb.

delmel · 22 Apr 2005

Ban all sheds

Supply an email address i will send you some info may help you when doing lighting design

delmel · 22 Apr 2005

Rotara

If you want my opinion between lov voltage v mains halogen then i will give it to you straight.

Lov volt every time because much crisper light, cheaper lamp replacement, fewer needed to achieve the same lumen output, longer lamp life (only if you use quality lamps and transformers) Do not fall into the trap of buying cheap crap ones. Mode or IBL would be my choice of transformer, fitting any make providing it has twist release for lamp change, lamp branded Osram, crompton, phillips, or prob best is BLV

5 x 50w LV = Approx 9 or 10 50w mains in terms of Lumin output

ban-all-sheds · 22 Apr 2005

felix said:
Here's something you might want to think about. Halogen lamps don't take well to being dimmed.

From the Philips lighting forum

"Low Voltage Dimming: Low Voltage halogen lamps should not be dimmed by more than 10% of their rated voltage since this will result in a reduction in life. Standard tungsten filament lamps (with no halogen filling), can be dimmed to zero volts, resulting in virtually endless life. However if low voltage tungsten halogen lamps are dimmed by more than 10%, the lamp will be operating at too low a temperature and the free halogens in the gas fill, will attack the cooler parts of the tungsten filament i.e. where enters the quartz or glass envelope. The wire at that point will then be eroded and eventually will fail. So if dimmed by 10% or more low voltage tungsten halogen lamps will not have an extended life but are unlikely even to reach their rated life."

They also don't like overvoltage, so if you go the mains halogen route, make sure you buy lamps rated at 240V, not 230V:

From the Philips lighting forum

"For every 1% change in supply voltage light output will rise by 3.6% and lamp life will be reduced by 12%.

Operating lamps at over 110% of their design voltage may result in rupture.

From http://www.blv.co.uk/halogen lamps instructions.htm :

"The lifetime of a tungsten-halogen lamp is strongly influenced by the voltage present at the base of the lamp. The lifetimes listed in the catalogue are always an average value determined in large-scale tests under laboratory conditions with regulated nominal voltage and a mains frequency of 50 Hz. In some cases, operation with overvoltage can considerably reduce the lifetime (e.g. by approx. 50% at 6% overvoltage)."

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Halogen >> Downlighters >> Transformer

breezer

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