Thread: downlights

Hi GeoffS

Originally posted by GeoffS
Cassandra
Can't resist commenting on this one -

I can't resist commenting on your comments javascript:smilie('')

Downlights
- the most inefficient form of lighting currently obtainable.
The lamps are inefficient (i.e light output for the electricity used)

No, they are actually more efficient than normal incandescent globes. They output more of a "whiter" light than a normal globe at the same wattage rating!

and the lighting patterns formed never seem to be where they are wanted.

Well that's not a problem with the light! That's a problem with the installer/designer.

- the thought of cheap and nasty transformers lying around in the ceiling makes any electrical worker's blood run cold.

Sure does, that's why good quality transformers should be used. The original "linear" transformers were prone to generating some heat and cheap ones would fail prematurely. However it is well worth paying the minimal extra cost for the "switch mode" transformers. These work in the same way as the power supply in a computer. These are _efficient_ and run cool. There is almost no loss via transformer heat etc.

- the lamps are expensive.

Yes, but the owners of downlights (those that like them) don't mind paying a little extra for the benefits _they_ perceive.

- a further fire risk comes from the use of low voltage, therefore high currents.

Yes, maybe but the risk is minimal, providing they have been "intelligently" installed.

Any loose connections are far more dangerous.

What LOOSE connections. There should be NO loose connections anyway!!!! Whether or not it is 12v or 240v!

- the lamps run very hot and in turn are close to the ceiling or in the ceiling, more fire risk.

Correct and thoughtful installation will reduce the fire risk to nothing more than ANY OTHER light.

I think many of your comments are misleading to others.

I have installed a variety of downlights in my home, including in a SOLID timber ceiling (which is the floor of the room above) I will post details and maybe some pics, in a subsequent message. Hopfully this will help potential other downlight users.

It only takes a little bit of thought beforehand to achieve a great lighting setup (BTW I am not a lighting designer, I am a very capable handyman).

Regards

Peter

Hi all

Please excuse the long message. It contains several quotes that take up space. I wanted to reply to several comments in various posts, so I combined them all into one message. (I hope I got all the quote highlighting correct)

Kind Regards

Peter

I think they are designed to bugger up, so you spend more on replacements.

Cheap halogens will not last as long as a quality unit - you get what you pay for!

If mounting into the cupboards: there are lights available which are about 30mm thick, they can be mounted into the bottom of your overhead cabinets if you fit a false bottom and router out reccesses.

They are available as small as 15mm x 55mm. Forstener bit or hole saw can easily create the opening required.

Perhaps it boils down to you get what you pay for but my experience with down-lights was not good. We installed them in a timber ceiling - looked great but very prone to over heating

I have installed eight 20watt halogens into my SOLID timeber ceiling - no problems.

Some of the newer transformers give better life because they run at 11.5 volts, greatly increasing bulb life (that .5 volt does make a difference).

Hmmm? This actually increases the current (amps) drawn through the wiring and throught the globe's filament. Given all things "electrically" speaking any addtional current though the globe would tend to decrease the life of the globe. If these halogen globes were to run at say 24v, then the current would be halved and the globe's lifespan _should_ increase. However there are many oher factors involved in the lifespan of a globe )

We found in hot weather the transformers would switch-off with the heat overload cutoff and take 15 minutes to cool down and come back on..... again the newer more expensive models are more stable.

Generally speaking the "more expensive models" are switch mode transformers. These are an "electronic" transformer they have circuitry inside them to control the output. They do run almost cold to the touch. There is a small disadvantage with this type of transformer in that it requires a "load", ie some wattage to actually run. Now however this is an ADVANTAGE in the use of downlights, if the globe fails then the transformer does not "switch on". It therefore does not waste electricity heating itself up as would the linear (older style) transformer )

The heat off the halogens also adds to discomfort in summer

This is a perception of heat. ANY 50watt globe puts out the same amount of heat. I mean 50 watts IS 50watts the difference is in the current used to create those watts!
You _may feel_ the heat more as the downlight concentrates the light and therefore the heat in more of a beam than normal incandescent lighting - however the heat is the same.

I would go for the bigger 240 volt downlights that have a reflective tube and use the energy saving bulbs - cooler and last longer - the downside is they take a while to come to full brightness.
Pity because I do find the light of the halogens better - especially with the eyesight not as good as it used to be.

They are cooler as they are usually of the flourescent type. This is also the reason why they last longer. A 20watt flouro uses the same amount of current as a 20watt halogen globe. The big difference is in the spread of light - oh, and the "whiteness" of the light (degrees Kelvin).

Hi BitingMidge
Don't buy the cheapest fittings you can find.

SOOOO true!

Use only one transformer per light fitting,

Not necessarily! You can obtain 105watt rated "switch mode" transformers and these can run 2 50watt halogen globes. Or you could, as I have, run 5x 20watt globes - WORKS GREAT for me!

and put dimmers on every circuit. If you drop back the power to the lights by about 15-20% you will find you have a much softer light, and apparently the darned things run 100% more efficiently.

100% more efficiently is bit out? Though they do use less current when dimmed therefore your electricity bill (efficiency?) is improved.

I don't pretend to understand the theory, but a 12v system is also more efficient electrically,

50watts of electricity is STILL 50 watts of electricity no matter how is is used. However the light output for a halogen globe at 50watts is brighter (whiter really) and more concentrated (directionally) than a normal 50watt incadescent globe. As this "whiter" light is reflected and concentrated into a "beam" the light is more efficient in _light output_.
[quote][b]
As per Mick's advice, there are a number of fittings designed specifically for bulkheads and which need as little as 35mm clearance.
FYI There are some light fittings - specifically designed for cabinet displays - that are only 15mm high and need an opening of 55mm and allow a MAXIMUM of 20watt globes

You will need somewhere to place the transformer, and make sure that you do install them in accordance with the manufacturers recommendations.

FYI Some of the newer switch mode power supplies allow up to 4 METRES between the globe and transformer - I assume that they are designed to provide a slightly higher output to make up for the voltage drop over that distance (at high current 4-5amps). If anyone decides to implement a distance such as this, please use larger cable, it helps prevent voltage drop and the drawing of more current.

Get in contact with a cabinet supply company, they will certainly have a product to suit your needs. off the top of my head, try Hafele, they have a whole range that is designed to be routered into 16mm melamine board.

Sometimes (most times?) the cabinet supply companies are a little overpriced for such items. Try some of the electrical wholesalers. I found Laurence & Hanson very helpful. I purchased via L&H 10 cabinet style halogen fittings (opening size 15mm deep x 55mmwide) for $10.00 each including a 20watt globe. Two 105watt electronic transformers will power all of these. Quality 105watt transformers are available for approx $25.00 each.

You may be amazed at what can be achieved with thoughtful use of these fittings - pics wil follow in another message.

again...

Regards

Peter

Originally posted by MrFixIt

FYI Some of the newer switch mode power supplies allow up to 4 METRES between the globe and transformer - I assume that they are designed to provide a slightly higher output to make up for the voltage drop over that distance (at high current 4-5amps). If anyone decides to implement a distance such as this, please use larger cable, it helps prevent voltage drop and the drawing of more current.

Ahh, assuming your transformer is constant voltage, introducing extra series resistance in excess wiring will reduce the current flowing not increase it. You WILL waste power in the wiring (volts dropped x current), the net effect being less voltage available at the bulb, which relates to less power and hence a dimmer light.

The voltage drop can only be minimised by larger cross section cable, but never ever prevented, (unless of course you have a superconductor and liquid nitrogen handy)

IMHO Halogen lighting is over-rated, watts is watts. Low voltage does not mean low power dissipation, it means high current.
Low voltage wiring can be a more serious fire risk simply due to the currents that are flowing. A poor connection at 12V will get much hotter than the same connection at 240V and the same wattage load (power = current * current * resistance).

The electricity companies use 220,000 volts in their distribution networks to help keep the current down, less current, equates to less power wasted in the high tension cables. The high voltages of course have their own problems.

Originally posted by zathras
Ahh, assuming your transformer is constant voltage, introducing extra series resistance in excess wiring will reduce the current flowing not increase it. You WILL waste power in the wiring (volts dropped x current), the net effect being less voltage available at the bulb, which relates to less power and hence a dimmer light.

Yes, I was assuming that the newer switch mode transformers can maintain a constant voltage - something like this must be implemented within its design, as the supplier makes a point of pointing out this 4 metre capability.

The voltage drop can only be minimised by larger cross section cable, but never ever prevented,

Of course, this is why I stated such in my previous message

"If anyone decides to implement a distance such as this, please use larger cable, it helps prevent voltage drop and the drawing of more current."

Kind regards

Peter

Hi Again

After rereading my message and the ...
"If anyone decides to implement a distance such as this, please use larger cable, it helps prevent voltage drop and the drawing of more current."

...part I realised that I SHOULD have written helps MINIMISE voltage drop, not "prevents" voltage drop. Wrong wording )

Kind regards

Peter

12volt Dichroic lamps are a wonderfull thing and are an excelent choice in their application.
such as feature spots, lighting art & garden lighting.

they are reasonably efficient and have good colour temperature.



BUT as a general source of houshold illumination they are dreadfull.

they have a bright white(ish) light that is strongly converged and tightly confined.

they are mostly used because they are cheap and easy to fit, and provide a flat cieling finish.

You can put 10 of these suckers in a kitchen and have a poorly lit kitchen wher ONE (thats "1") 40 watt fluro would do a much better job.

for good confortable houshold lighting you need a portion of direct and a portion of reflected light, all of dhich should be difused.

Down lights of any form would have to be one of the most frequently and worst applied building product of all time.

have a look at a nice circular fluro oyster fitting.

Hate down lights die die die!!!:mad:

If you want irritating poorly difused, glare filled, expensive to run lighting, install dichroic down lights.

A 50 watt dichroic down light is equavalent to an 80 watt portaflood.
would you put 10 portafloods in your kitchen???

Dimming halogen lights.
Halogen lights do not like being dimmed, they are designed to runn hot (too complicate to explain "the halogen cycle"). If you dimm them below about 85% capacity they willl blacken & die early.

better to use a wider angle lamp and a lower watage.
there are 4 availeble beam widths and 20 and 50 watt versions.

did I say i hate down lights.

So Soundman hates downlights!!

While we are all entitled to our views on what does or does not constitute good lighting design, a couple of statements above cannot pass unchallenged!

1) Of halogen lights "They are reasonably energy efficient". I don't pretend to understand the maths, but most catalogues claim a reduction of up to 75% over an equivalent wattage incandescent without dimming. I guess consuming a quarter of the electricity is "reasonably efficient" so can't take you to task! Certainly they are not as energy efficient as fluorescent fittings, but there are certain ahem...aesthetic considerations here as well!

2) Dimming. The attached image is from the OSRAM/sylvania catalogue. A search of any manufacturers catalogue will show similar figures. Basically these indicate that significant savings and increases in lamp life can be made by reducing voltage slighthly. Beyond 80% the graphs flatten out, and below about 30% the lights don't seem to operate. Effective dimming visually is usually in the 80-90% range which is enought to soften the harshness of the light.

3) How many FLUOROS are equal to an 80w portaflood, and who cares?
As I have said in an earlier post, we have three (3) halogen fittings in our kitchen apart from the light over the range hood, and have no lighting challenges. I guess it's just a case of paying for the right advice rather than experimenting! The lighting is not even, but provides sufficient task lighting for all preparation and cleaning tasks. Two more fittings would have evened the lighting pattern, but we don't need five Portafloods in our kitchen!! (sorry!!)
No glare, no diffusion, not expensive to run.

4) Fluorescent fittings:
I've never seen a "nice" fluorescent" fitting!! And I love the control one gets over lighting levels and the green tinge to the meat unless one uses daylight globes which make everyone look artificially suntanned.

Did I say I hate fluoro fittings??

5) "they are mostly used because they are cheap" AHA! The crux of the issue.....DON'T use cheap if you want a flexible lighting solution that you can enjoy. Cheap will pretty much achieve all the negatives you claim, and will save as little as $20 per fitting.

Yes they do provide a flat ceiling finish, which in itself is reason to consider them in some installations.

Finally.....if you fitting out a seriously retro house or are stuck in a 60's time warp, use fluoro's everywhere. (We used to do these wonderful pelmet fittings covering 40w tubes). If not, I suggest you do a heap of research and you'll find as I did recently, that times have changed and there are newer flexible solutions!

Cheers,

P

Well, Every beast to its own devices.

Few comments on low voltage halogen lamp life:

1) good quality electronic transformers increase lamp life by limiting initial current.

2) Running lamps on full power once in a while helps with the halogen cycle and reduces lamp blackening / redepositing tungsten on the filament thus increasing effective lamp life.

There are florescent lamps / fittings with all the features of low voltage halogens. But they are much larger (160mm dia, 200mm deep), much more expensive and require 10V dimmers and associated control gear to match LV halogen's features. More appropriate for commercial applications.

Regards,

Theva

My apologies if I seemed grumpy in the above post! Seems I write grumpy early in the morning.......grumpy not intended.

Thanks for the advice re running at full power once in a while...can't say that I've ever experienced lamp blackening but will watch out with interest.

Cheers,

P

All light fittings have their place (some that place is the bottom of a skip) the most commom problem is the failure to design (at all).

Most lighting fitting selection is not basses on performance but on appearance or other factors.

There is a big backlog of bad feeling toward the fluro due to bad application in the past dating back to the 50's.

In years to come the same unjustified bad feeling will apply to down lights for the same reasons.

Big mistakes with down lights.
they are not suitable everywhere.
too many
too bright
too close
no difuser fitted
fitting selected on appearance turned off.

improvements in fluros
better selection and quality of colour output
longer life
better efficiency
no longer contain mercury ( well shouldn't)
more shapes & forms of lamp available
much better range & quality of fittings.
fluros are more efficient than most other forms of houshold light

any body who puts up a basic straight fluro in a nice house should be slaped arround the ears with a stale mullet.

remember the old fashoned light bulb still has a place and may still be the best choice in some situations.
they have a warm colour temperature
tolerate dimming realy well
burn in any position
are cheap as chips
come in a vast array of shapes, forms & wattages.

I waiting for some of the new foprms of light to mature.
high intensity led looks very promising.
electro-luminessent panels & wires could be very funky.

I'm not a real fluro lover either but they still produce the all round most usefull light for domestic applications.

cheers

[QUOTE]Originally posted by MrFixIt

Hmmm? This actually increases the current (amps) drawn through the wiring and throught the globe's filament. Given all things "electrically" speaking any addtional current though the globe would tend to decrease the life of the globe. If these halogen globes were to run at say 24v, then the current would be halved and the globe's lifespan _should_ increase. However there are many oher factors involved in the lifespan of a globe )


This was in response to 11.5v increasing globe live. This is right more voltage more current though globe shoter life. 24v thought same resistance twice current glob dead.

biting midge

Which catalogues claim that halogens use 25% power for the same light output?
This is just plain wrong.
Halogens use fractionally less power for the same light output as a standard incandescent, but it is very marginal and does not include transformer losses (which are also quite small in the switchmode transformers.)
So overall the halo and the incandescent are about the same for energy efficiency. Except that downlights require ventilation artound them to stop them cooking, which means holes in your ceiling insulation, so your heating and cooling costs are higher.

The technology of a halogen is basically the same as incandescent, except that the halogen gas allows the filament to run hotter, so it produces a whiter light. A standard incandescent could be designed to burn that hot and it would produce just as much light, but it would soon burn out.

Chris.

Hi

Just a quick post to let you know I have updated my home page. A rare event <g>. The update shows images of some of my "shelf" or cabinet lights in use as down lights. The images do not convey the lighting effect very clearly, in that the images are not as bright as I would have liked. Please bear in mind that in real life the lighting is very good. (Some of the links do not work correctly, however you should be able to see all of the images via clicking on the thumbnails).

Please feel free to ask any questions and I will help in any way I can.

Go here

http://www.multiline.com.au/~psander...k/woodfram.htm

and click on downlights

or Mobile base if that interests you.

Kind regards

Peter

We ahve just installed 240v halogen 'spot' lights in our kitchen to illuminate the areas that the fluoro misses.
They are like 4 little super troupers on a stainless track and rated at 50w each.
Given they are directional I found I was able to direct two to cover a wide area without creating a shadow when standing in front of the light.
Admittedly the setup cost in excess of $200 but the little lights work well and with their own little UV shields do not create a sunburnt neck problem.
I can feel the heat on the back of my neck but it is not 'that' hot, and at my age, almost therapeutic
I wired them in to the normal circuit and they are switched with the centre switch on a two outlet power point, this is probably safer than the lighting circuit as there is a circuit breaker, earth leakage detector on these circuits.
The lamps are about $5 each and come with their own reflector and lense.
We only use the lights when ligyt is low and we are working at the kitchen benches.
Just my 2.2 cents woth incl GST.