Downlighter facts.

[homealoan]

Hi

I'm looking in to having some of the dreaded downlighters fitted but am really confused by all the different types and running cost etc. Could someone perhaps clarify the following points, please?

(1) Can halogen lamps be dimmed?

(2) Can the low voltage transformer ones be dimmed?

(3) Is it cheaper to run a 12v 50watt lamp than to run a 240v 50watt lamp?

(4) Does a circuit running a 12v transformer connected to a 12v 50watt lamp use less current than a 240V 50watt lamp?

(5) What wattage of energy saving CFL lamp would give the same "brightness" as a 50watt halogen lamp?

(6) Is it true that low voltage ones regularly trip circuit breakers when they're first switched on - something to do with a surge of current - and that it may mean having a different type of circuit breaker fitted?

Thanks

 

[jj4091]

1 yes. 2 some of them. 3 No. 4 no. 5 11w. 6 no.

 

[homealoan]

Just what I was hoping for; a straightforward no nonsense reply that even I can understand - brilliant!

Thanks very much

 

[Softus]

(4) Does a circuit running a 12v transformer connected to a 12v 50watt lamp use less current than a 240V 50watt lamp?

It's an odd question, but the answer is that it will draw (not "use") more current, not less.

 

[ricicle]

(6) Is it true that low voltage ones regularly trip circuit breakers when they're first switched on - something to do with a surge of current - and that it may mean having a different type of circuit breaker fitted?

Thanks

Wire wound transformers can trip MCBs with lower instantaneous trip ratings when first switched on, but not always - it depends on which part of the AC cycle that the circuit was switched on

 

[BS3036]

It's an odd question, but the answer is that it will draw (not "use") more current, not less.

But not significantly more.

 

[Softus]

Define significant.

 

[Spark123]

50w @ 240v is approx 0.2A.
50w @ 12v is approx 4.2A. The higher current will be on the 12V side of the transformer, the 240v side of the transformer will draw approx 0.2A not considering transformer losses.

 

[Softus]

50w @ 240v is approx 0.2A.

To be picky, it's closer to 0.21A, but to fair you stated it to only one decimal place.

50w @ 12v is approx 4.2A. The higher current will be on the 12V side of the transformer, the 240v side of the transformer will draw approx 0.2A not considering transformer losses.

True - if you ignore the factor(s) that make it different, then it will be the same. However, in reality, it will draw more than the equivalent 240V (i.e. GU10) bulb.

I really don't see what the discussion is about. The OP asked if the current would be less, and the answer is 'No - it will be more'. If he had asked if it would be approximately the same, then the answer would have been 'yes'.

 

[Dippy]

5) Depends on the angle of the diffractor. IMHO, all 50W halogens that I have tried (and I have tried a few) give off more light than an 11W CFL. However it is subjective and I recommend that you try sample lights for yourself.

Also the Osram IRC halogens are excellent. Again IMHO, the 35W IRC is brighter than the 50W non-IRC (for the same angle).

In my house I will be using a combination of IRC halogen and 11W CFL downlighters (on a Flexidim system) so that I can have the advantage of dimmed light for scene-setting, but be as energy-efficient as I can be at the same time.

 

[homealoan]

Thanks for all the replies, they're very helpful. Just one more question(!) If I want to dim 12 volt downlights will I need to buy a special type of dimmer as well as a dimmable tranformer?

Thanks again.