Replacing 12v with 240v downlights

[dk1uk]

Hi - I need to replace 7 x 12v downlights with 7 x 240v mains downlights. I know that the current set-up is OK because it was tested/approved by a Part P electrician as part of some recent building works.

I realise to some that this might sound like a silly question, but is what I'm planning to do potentially exceeding the permitted wattage of the circuit? Can I just remove the 12v transformers and connect the new downlights or will my new 240v downlights make a bigger demand on the circuit?

Any help much appreciated.

 

[Porque223]

[Neglecting transformer losses] at least one website seem to say that the higher voltage bulbs convert elec. to light more efficiently, higher luminous efficacy, and so for the same lux illumination values you'd pull less power.

 

[EFLImpudence]

is what I'm planning to do potentially exceeding the permitted wattage of the circuit?

It's all down to the wattage. 12V or 240V makes no difference.
6A circuit will be 1380W - including other lights on circuit, of course.

Can I just remove the 12v transformers and connect the new downlights

Yes.

or will my new 240v downlights make a bigger demand on the circuit?

Not if the wattage is the same.

 

[RF Lighting]

[Neglecting transformer losses] at least one website seem to say that the higher voltage bulbs convert elec. to light more efficiently, higher luminous efficacy, and so for the same lux illumination values you'd pull less power.

That's not correct.

50W 12V lamps are brighter than 50W 230V lamps.

 

[Taylortwocities]

Maybe its different when the frequency is 60Hz instead of what everybody else uses

 

[ban-all-sheds]

[Neglecting transformer losses] at least one website seem to say that the higher voltage bulbs convert elec. to light more efficiently, higher luminous efficacy, and so for the same lux illumination values you'd pull less power.

Which website is that?

 

[Porque223]

[Neglecting transformer losses] at least one website seem to say that the higher voltage bulbs convert elec. to light more efficiently, higher luminous efficacy, and so for the same lux illumination values you'd pull less power.

That's not correct.

50W 12V lamps are brighter than 50W 230V lamps.

Then their efficacy must be greater so maybe the transformer losses with the 12v system more or less equalizes both options.

Can you post a link for this?
Is this perceived brightness or actual brightness? Although I guess it's the perceived brightness that counts.

 

[ban-all-sheds]

AIUI, ELV lamps have thicker filaments, and run hotter, so the light tends to be "whiter" (perception) but also you do get more lm/w (actual).

That said, I'd not be surprised to learn that good LV ones outperform poor ELV ones.

 

[RF Lighting]

[Neglecting transformer losses] at least one website seem to say that the higher voltage bulbs convert elec. to light more efficiently, higher luminous efficacy, and so for the same lux illumination values you'd pull less power.

That's not correct.

50W 12V lamps are brighter than 50W 230V lamps.

Then their efficacy must be greater so maybe the transformer losses with the 12v system more or less equalizes both options.

Can you post a link for this?
Is this perceived brightness or actual brightness? Although I guess it's the perceived brightness that counts.

Closest match I could find for comparison:

12V lamp

50 W 12 V 36° GU5.3 Luminous intensity 1450 cd



230V lamp

50 W 230 V 35° GU10 Luminous intensity 650 cd

 

[Porque223]

I'll have to bookmark this - it's not even close and the OP is maybe rightly concerned.

1450 >enter BCP
36 >enter BA
446 =calc'd lumens
50 >enter watts
9 =calc'd lumens/watt efficacy

650 >enter BCP
35 >enter BA
189 =calc'd lumens
50 >enter watts
4 =calc'd lumens/watt efficacy

Not great efficacies.

 

[bernardgreen]

ELV lamps can have shorter filaments which results in a smaller area of light production which enables better focusing into beams as in spotlights and similar fittings.

LV (230 volt) lamps have longer filaments and hence are not so easy to focus.

The efficiency of all lamps depends on what use they are designed for.

High efficient lamps tend to run white hot filaments, have short life times and are often intolerant of voltage variations.

Long life lamps are often warm white with filaments not run at white heat. they often have long life times and are very tolerant of voltage variations.

 

[ban-all-sheds]

Mind you, it is all a bit like agonising over whether a Toyota Landcruiser Amazon has better or worse fuel economy than a Cadillac Escalade...