Downlights with a combined power greater than 1200 Watts

[oharaf]

If you had mentioned that there were tranis in the first place it would have been far easier to advise you.

All the advice you've been given is good, halogens dead hot and LED's don't like tranis.

You should be fine

Diversity is 66% if my brain recalls correctly

 

[electronicsuk]

And 12 volt lamps use more energy than mains voltage lamps. This is due to losses in the transformers. Each lamp will probably use 52 watts in total in real terms.

It's down to personal preference, but in my experience, 12v halogen reflector lamps give a far better light output than their mains counterparts. Watt for watt they seem brighter, and the light seems to be far more evenly spread, probably due to the difference in filament thickness between the two. I'd say they more than compensate for that couple of watts lost in the transformer.

i accept the wasted power/ environment issues with the halogens...and maybe a decent LED might be developed/tried...I have offset some of the environmental issues with water recycling in regards to rain water collection for lavatories, garden tap and washing machine etc...also suspect that softer room lamps will be used (but i'm not the interior designer...i just do as i'm told) (sorry if i anger any environmentalists)

If you're prepared to part with the cash then LEDs are ready to replace halogen lamps right now. Take these, for example. Roughly equivalent to a traditional 40w halogen, but consume 1/10th of the power. Don't confuse these with the cheap lamps on sale in DIY sheds that use ten or fifteen 5mm white LEDs inside a reflector fitting, as there really is no comparison.

Matthew, Diversity, sorry!!!!!

No need to apologise

 

[mattysupra]

are you certain 12v stuff pulls the same power?

( im not a sparky!!! )

I was under the impresion that 12v stuff pulled alot less power. For instance on our boat it has loads of 12v downlighters. Now these run of the engine or battery's when out at sea (anchored) . When your at a marina you plug in the mains and it switches over to a big charger that will supply 2 fridges,, all the lighting, showers, central heating, toilets and then charges 5 huge batterys, there is also the t.v/dvd/sat and all the radar and masses of other stuff running off it.

The battery charger will only give out 30 amps of power 12v. to do all this. It will however supply something like 300 amps to crank the engines if all the battery are flat for some reason.

Now if all this 12 volt stuff pulled so much power, would they not be better sticking all 240v stuff in and having a invertor powering it out at sea?

Or do inverters really pull massives of power?

We have invertors (guess its a invertor as have some 240volt sockets that provide 240 with no shore power) onboard also to power hair dryers etc when out at sea that run of the battery but never had one flattern the battery yet.


maybe the main charger pulls alot more power than i think it does/the dials tell me. I know it costs peanuts in electric to run for a month none stop on shore power (15-20 quid a month) where my house that is energy efficent compared to a boat costs me 150 quid a month with less lights to power and alot of things like water that comes out and drains without the need for electric!


Sorry for stealing the thread !

 

[Wet5park]

Thank you to everyone for your answers, advice and concern.

Its unfortunate that i didn't discover this forum prior to starting my building project, however i am where i am, in that we have decided on Halogen downlights (which i know are hot) based on the desired look and low voltage was used due to the required lighting effect.

Cool fitting Halogens (which i know are still hot) are being used to reduce 25% of upward heat and using an ultra compact fire rated downlight. I accept that the Halogens aren't everyones choice, and thanks for the advice rather than critisism on my choice of lights.

I think i now have the answer to my initial question, although will start another topic in regards to calculating the wire thickness in regards to other applications.

As i understand it a 6amp MCB will be sufficient based on a 230/240 voltage supply (6x230 = 1380w)...the max watt will be 1350, but the halogen light i'm likely to use will be 40watts or less...therefore based on everyones comments i should be ok with a 6 amp MCB and 1.5mm cable.

Thanks for the info in regards to the switching and i can confirm that switches are 10amp (if i were to use a 10amp MCB), however the dimmers state 210 watts max on the transformer...this therefore raises another question in regards to having 7x50watt halogens on 1 dimmer?

Finally i accept its very unlikely that my house will be lit up light a christmas tree all the time, however some of you have mentioned "Diversity"...what is meant by this ?(i've had a guess but would welcome an exact answer)

I have assumed that the circuit should cater for all the lights being on at once (worst case), max power....is this wrong, and is this where diversity comes in?

Thanks again

 

[mattysupra]

if you use a 6amp mcb, what is the worsed that can happen??? It will trip?? If so then jump up to a higher one if cable will permit.

Think you will need bigger dimers tho if you going past there rating!

Im not a spark by the way! so could be speaking ****** here

 

[ColJack]

watts is watts is watts...

Watts = voltage x current..

so
50W at 230 = 0.2A
50W at 12 = 4A

 

[sparkyspike]

I was under the impresion that 12v stuff pulled alot less power.

They don't. As power is voltage x current, 12v lamps draw more current than 230v lamps. The power remains the same.

I don't think 25 downlights are particularly excessive. Ok, there are alternative lamps you can use to reduce running costs, but in my opinion, they are not as effective. Some are useless.

Having 25 transformers in your ceiling could cause problems with radio interference, so maybe consider using 230v - they're not as bright as 12v though.

 

[17thman]

watts is watts is watts...

Watts = voltage x current..

so
50W at 230 = 0.2A
50W at 12 = 4A

so 2x50w 12v haolgens is too much for you average mcb?

 

[flameport]

so 2x50w 12v haolgens is too much for you average mcb?

If it was a 6A MCB and in the 12 volt circuit then yes.

 

[17thman]

that was my point

 

[ColJack]

to get 50W out, you have to put 50W in..

0.2A into the transformer at 230V
4A out of the transformer at 12V..

 

[bongos]

Finally i accept its very unlikely that my house will be lit up light a christmas tree all the time, however some of you have mentioned "Diversity"...what is meant by this ?(i've had a guess but would welcome an exact answer)

I have assumed that the circuit should cater for all the lights being on at once (worst case), max power....is this wrong, and is this where diversity comes in?

Diversity is where you take into account the likelihood that all loads on a circuit are switched on at the same the same time.

For example, your ring final circuit is likely to be protected by a 32A MCB. If you plugged in all the stuff you had and switched it all on it is likely that it would overload the circuit and trip the MCB. But this doesn't normally happen. Taking into account diversity you would rarely be drawing that amount of current on that circuit.

I'll admit that I didn't think you could take diversity into account on lighting circuits but from reading above it seems that you can.

 

[ericmark]

1) As already stated limit for 6A fuse is 1380W and there is also likely some diversity.
2) Although one can use up to 16A see 559.6.1.6 we must also abide by 559.4.1 which says we must follow manufactures recommendations and most ceiling roses are only rated at 6A so in most cases we are still limited to 6A.
3) 422.4.2 requires a minimum distance from combustible materials of 0.5 m for small spotlight or projector unless otherwise recommended by the manufacturer. In many cases this preludes the use of small spot lights in the ceiling.
4) 44 in Part L1B document requires 40 lumens per circuit-watt and the small 50W spot light does not comply.

I would agree it seems daft that the DIY sheds can sell items which you can't use but because you could be buying for export there is nothing to stop shops selling items which you can't use in this country. In Hong Kong one needs to show passport to buy anything you can't use in Hong Kong but we don't have those rules here.

 

[ElectricDunc]

3) 422.4.2 requires a minimum distance from combustible materials of 0.5 m for small spotlight or projector unless otherwise recommended by the manufacturer. In many cases this preludes the use of small spot lights in the ceiling.
4) 44 in Part L1B document requires 40 lumens per circuit-watt and the small 50W spot light does not comply.

Regarding point 3 which you've made in another post, doesn't this only apply to the surface the lamp is projecting light on to. The manufacturers instructions on non fire rated recessed lights is an air gap of 100mm from the rear of the lamp and atleast 20mm from the edge of the fitting to any surface. I've only ever come across a property with a 0.5m floor void when working on a stately home!

As for point 4, Part L of Building regs won't apply unless it is a new build or part of a property where the building has been altered (extended). Similar to the way Part M doesn't apply in a rewire or addition (i only know this from an interesting topic/disagreement with BAS! )

 

[plugwash]

I'll admit that I didn't think you could take diversity into account on lighting circuits but from reading above it seems that you can.

According to regs you can. I would advise against it though in most normal situations. If a building is fully occupied there is a good chance all lights will be on at once.

The one time I might consider it reasonable was an installation with very large numbers of lights where some rooms had more than one set of lights and the different sets were not intended to be used at the same time.