Advantages of 12v downlights

[ringer]

Customer has 12v downlights in the kitchen and is concerned because they are very hot. Too hot to touch. Additionally they have some ventilation problems in the roofspace above (single storey kitchen with loft space) which I am separately sorting out.
Am not too clued up on lighting, out of choice of 230v GU10 / LED / 12V GX5.3
can someone who is clued up please explain the advantages of 12V over the other two types. Also need to reassure customer that although they are hot, it is not a problem as long as you don't try to touch them - is this correct? GX5.3 are backward heat - what does this mean, and is there implications about heat dispersal above the light? Am considering fitting firehoods as part of ventilation solution.

 

[ringer]

thought I ought to do a bit of research for myself so just did a quick google on 'backward heat'. Ten minutes after I posted this new thread - this actual thread appeared as item 4 on the google search results


but don't let that distract you guys from answering my question please

 

[DiscoDave]

All lamps (led excluded) will be too hot to touch during normal operation, that's part of the reason they are so in-effiecient as they give out so much heat. GU10 lamps are no different.

Why 12v? Personally I think they give a better light and the lamps last longer with a soft start transformer.

What are the ventilation problems? and how would a fire hood help?

 

[ringer]

Ventilation problems:
Originally loft space above kitchen had no ventilation (false holes, no actual ventilation). So customer had vent holes put in, one each side to allow through draught. Now getting large amounts of condensation on roof struts in this very cold weather. Customer has loft insulation installed to current regs (270mm +) on floor of loft space. Each downlight has plasterboard box over it to keep off loft insulation, but each box has two large holes in top to allow heat to escape (their previous attempt to keep down temperature of lamps). Loft insulation surrounds boxes, but is not over the top of them. Hence lots of heat rising, causing condensation as heat hits very cold sarking felt and roof struts. Also breaks the fire barrier - not good.
My solution - accept that lights get hot. Fit fire hood over lights while retaining existing boxes. Cover top of boxes with loft insulation. Alternatively, Electric Center do Joist brace kits that will do the same job (page 264 in the EC catalogue). Spoke to local authority Building Control about the ventilation and they said as well as side vents, loft space needs vents in the roof. They suggested replace two tiles with vent tiles.
All this ventilation means I can't sell them lights and charge them for fitting (and there is no RCD at present, so would have been extra work there), but hopefully this will build up good will for future jobs. They are fairly affluent - my favourite kind of customer!

 

[DiscoDave]

I see where you are coming from, the ventilation problem is to do with the loft space, not the lights getting too hot. I'm not to sure how to overcome the condensation problems however fitting aluminium or foil backed lamps may help to reduce the temperature in the loft space.

 

[pennywise]

You could put these in, then just reinstate the rock wool over the tops of the fittings and remove the baffle boxes , you would however have to replace all the trannies as well to the insulation coverable ones.

Aurora - 'Passionate about Lighting'

 

[ringer]

They look quite good - nice spec - but the lady of the house insists on gold colour to match everything else in the kitchen. Would have to extend wiring to each light - existing cables only reaches two transformers, 3 lights on one, four on the other. Each of these Aurora lights has their own transformer - but they are dimmable though! And seeing as how there isn't really a problem with the existing lights, I'm not too sure they will want to shell out £200 for new ones just because they are a better spec, no matter how affluent they are.

 

[Deleted member 9648]

Re-condensation...I once had a bungalow with a large open roof space which had shocking condensation in cold weather,it almost looked like it had rained on the insulation below. I added soffit vents and cut air vents into the gable ends,it made not a scrap of difference. I believe it was due to the type of concrete tiles and the way the roof was inclined,and was just something I had to live with.
12v 50w lamps are considerably brighter than 50w GU10,which I believe to be only equivalent to a 12v 35w,the quality of light is also superior with 12v.
12v dichroic lamps are 'cool beam'...the heat is lost from the lamp itself and not thrown forward,this can be an advantage when spotlighting heat sensitive things,but means the lamp itself gets extremely hot. Aluminium reflector lamps are also available and project heat forward so the lamp does not get as hot as dichroic,but still very hot.
The main disadvantages with 12v is that they are high maintenance,transformers and lampholders both commonly fail,and those without the ability to go beyond changing the lamp may find themselves calling the electrician regularly.....I think it is worth pointing out both the pro's and cons of 12v lighting to clients at the design stage. I've had several customers with large numbers of 12v downlights who have told me if they had been aware of how high maintenance they were they would not have had them.

 

[sythai]

Never really gone for the 12v setup as hassle of maintenance, but have no choice on a job coming up....

Reason being the customer wants a defined spot light set up and only 12v dichroic go down to lower enough degrees, have found a 10 degree lamp, can't get anywhere near this in GU10.

 

[pennywise]

I always try and point my customers down the GU10 route far less maintenance and easy to swap the lamps to LED's or CFL lamps when they want to save the world. Brass nice!! lol. They where only a thought, more to solve the condensation problem didn't realise you had multiple lights wired of on trannie.

 

[telectrix]

personally, i would do a bit of rewiring, scrap the trannys, fit GU 10 fittings with kosnic 5w LEDs. job done, no heat, low maintenance.

 

[Des 56]

Advantages of 12 volt downlights

Urm lets see now
They are urm
Well perhaps,maybe, no

I dont know Ringer,you are going to have to tell,cant think of one at the moment

 

[Bright Sparks]

Pro's

GU10 - less time to fit, cheaper.
MR16 - More light output (almost double the lumen output vs GU10), 12v (Safer for end user)

Con's

GU10 - when they blow they have a high inrush current which often 'blows' dimmers and or the MCB. Manufacturers have tried to counter this by fusing both the legs but this doesn't always work.
MR16 - Extra cost in the form of a transformer, with more 'potential' to go wrong. I always use the AU-E60 from Aurora Aurora - 'Passionate about Lighting' it is a premium transformer but has a 10 year warranty and I have rarely had one go wrong.

Saying all this I am installing more GU10 style fittings as more and more people are requiring 'low energy' lighting there is less hassle with these in the GU10 format.

Hope this helps

 

[Bright Sparks]

Opps forgot to mention heat.

50w halogen reach over 200 Deg C at the surface, one of the downsides of tungsten halogen lighting, there is no way around this except use low energy lights such as Compact fluorescent (CFL) or LED technology.

The heat has to go somewhere and heat rises, this takes with it the moisture in the air, which can be considerable in kitchens, up in to the roof void. Hence the condensation.

LED and CFL do get hot but no where near as high, LED lamps for instance have a working temperature of around 80 Deg C