Downlighters in Bathroom

[Terry2sheds]

Hi,
I see several posts on this subject, but none actually answer my questions exactly.

Apart from the debates about the type of light produced, Is the benefit of 12v lights over 240v that they are safer?

I see the calculation that current = Power / Voltage, basic Physics, but if using say 7 x 35w downlighter on 12v transformers, is the calculation 7 x 35/12 or 7x 35 /240?
If it's divided by 12 then these lights would need a 21 amp minimum fuse, whereas we're talking only 1.02 amps divided by 240.

 

[ban-all-sheds]

Does your basic physics knowledge not extend to primary and secondary sides of transformers, and the relative voltages and currents?

 

[Terry2sheds]

Obviously not or I wouldn't be asking.
Perhaps I was in the sarcasm class at the time.

 

[ban-all-sheds]

OK - think logically.

What does a transformer do?

If you took one of those 12V lights and connected it to a car battery, would it be about the same brightness as it would on the transformer?

 

[Terry2sheds]

Admittedly, but thta's not what I'm trying to establish.
I've read on other posts that the current is greater for 12v lights, but logically I would have though that the actual current from the 240v system to the transformer would only require the same current as a 240v lamp. Correct?
I then assume that this is why the build up of heat in the Transformer ?

I just want to be sure that I won't overload upstairs lighting circuit MCb.

 

[ban-all-sheds]

I've read on other posts that the current is greater for 12v lights,

To deliver 35W at 12V requires 2.92A.

To deliver 35W at 240V requires 0.15A.

but logically I would have though that the actual current from the 240v system to the transformer would only require the same current as a 240v lamp. Correct?

Virtually - there will be some losses in it, so it'll need a fraction more.

I then assume that this is why the build up of heat in the Transformer ?

Unless it's making a noise as well that's where all the losses go.

 

[Terry2sheds]

Thanks for the help.

I know downlighters seem to be frowned upon on this forum, but if you were fitting them, would you use the 12v or the 240v?

 

[ban-all-sheds]

Neither.

 

[Terry2sheds]

Well, assuming as in my case that your daughter wants them, and putting aside personal issues with them, which then?

 

[ban-all-sheds]

Neither.

 

[aptsys]

I've got some 12V types that were installed 10 years ago and still haven't blown once. GU10's seem to blow all the time.

 

[Terry2sheds]

Thanks Aptsys, That answers the question.

 

[Chri5]

Terry

50w spots are an expensive form of lighting. If 6 are needed and used 8 hours a day (unlikely) the cost is in the region of £14 x 6 = £84 pa.

Why not go led lamps, 3w @£9 each for very gentle (eqv approx 20w) and 6weqv approx 35w) @ £20 each.

LED lamps are available for LV 230v and ELV 12v spots.

6 based on 3 x 3w and 3 x 6w would save £70 pa + of the £84 mentioned.

So lamps pay back (3 x £9 + 3 x £20 = £87) is just over a year, the products suggest 20,000 hours of use.

At 8 hours a day that's about 7 years

 

[Terry2sheds]

Well,
I've got to admit that I didn't realise just how much could be saved by using LEDs, but as this is in a bathroom, it's unlikely to be used for an hour a day.
I'm proposing to use 35w lamps, so at 1 hour per day, the cost per annum is likely to be nearer £7 than £84, so the initial outlay would take many years to recoup, although the LEDs would last about 50 years!
If I were installing in a room where the lights were on 8 hours per day, say in commercial premises, I would seriously consider LEDs.

 

[RF Lighting]

Definately go with 12V lamps.

The light they produce is far superior than the 230V equivalent.