12v conversion of 230v light fitting.

marcuswareham · Apr 17, 2020

Hello,

I am wondering if this is allowed, I dont have a big need to do such a thing, just would like to know how it would stand up with the law and regs etc

If you have a class 1 (or class 2 for that matter) light fitting and you wanted to convert it to 12v to make it PELV, for use in an old house with no CPC in lighting circuit or in a special location etc

It is very easy to do, as B22 and E27 bulbs come in a range 12v versions (typically used for boats or motorhomes). So swap the bulb and then supply it via a safety isolation transformer of correct voltage and label up appropriately, after checking wiring is appropriate for the current at 12v + overcurrent protection on 12v side

I am thinking that there could be a problem with this as the light fitting was sold as a 230v fitting and therefor tested to be exactly that, however by you changing the voltage would you in effect be liable for any faults with that light whether it is the fault of the 12v or not and the like

Thanks Marcus

telectrix · Apr 17, 2020

if you were using a fitting at a voltage above it's rated capacity, it could be a problem. reducing the voltage can't cause any trouble as long as you allow for the fact that the current is 20 X @ 12V as it is @ 240V.

marcuswareham · Apr 17, 2020

telectrix said:
if you were using a fitting at a voltage above it's rated capacity, it could be a problem. reducing the voltage can't cause any trouble as long as you allow for the fact that the current is 20 X @ 12V as it is @ 240V.

yes thats my thinking of course would need to be labeled up and wire size checked

how would commission such a thing although, what would be on the cert

freddo · Apr 17, 2020

If I was doing this I'd probably choose 36V. As mentioned above the current drawn would be large quite large at 12V and the volt drop would be a problem. Bit easier now with LED though. Certainly unconventional, would need a really really good reason to avoid rewiring the circuit.

marcuswareham · Apr 17, 2020

I see your point with the voltage, although with LED bulbs now which draw so little it can be achieved easily.

yes like you say in most cases you would run a new cpcs in or use appropriate double insulated or PELV fittings

could be handy of there were some nice looking class 1 outside lights on a PME supply on easy reaching distance of say a hot tub on TT

westward10 · Apr 17, 2020

If the circuit/s do not incorporate cpcs how will you earth the isolating transformer.

marcuswareham · Apr 17, 2020

westward10 said:
If the circuit/s do not incorporate cpcs how will you earth the isolating transformer.

Good point!

As i understand it requires and earth in the regs incase of insulation fail and therefore not electrically separated. Is this still the case with a safety isolation transformer with extra insulation.

I guess the fact its extra low voltage doesn't negate the eend for earth

westward10 · Apr 17, 2020

It is possible you can get an encapsulated transformer which is Class II however it's point of connection is likely to require a cpc. It should be noted Class II protection in a dwelling is not realistically practical as it is not under the supervision of skilled persons.

pc1966 · Apr 17, 2020

If the problem is the lack of CPC in the lighting circuits, and the current for 12V (or 24V, whatever) is within the rating of all existing cable/switches/sockets, then the only issue for earthing would be any electrostatic shield (if output floating, probably a bad idea) or the secondary winding for the isolation transformer.

But that transformer could be near the existing CU so all cables for lighting (without CPC) are just moved over to the low voltage supply, and the transformer is earthed at the CU location by whatever means necessary.

marcuswareham · Apr 17, 2020

pc1966 said:
If the problem is the lack of CPC in the lighting circuits, and the current for 12V (or 24V, whatever) is within the rating of all existing cable/switches/sockets, then the only issue for earthing would be any electrostatic shield (if output floating, probably a bad idea) or the secondary winding for the isolation transformer.

But that transformer could be near the existing CU so all cables for lighting (without CPC) are just moved over to the low voltage supply, and the transformer is earthed at the CU location by whatever means necessary.

I do like that thinking, would mean you wouldn't need to run a CPC in

However still not sure if it acceptable to change 230v fittings to a lower voltage, would that in effect make you the manufacturer

pc1966 · Apr 17, 2020

If you are simply installing standard lamps that are low voltage and below the current limit for the fittings I don't see any problem. The main issue has already been mentioned, that the current will be 20x or so, and that would be the issue that would bother me.

But still, a 12W LED bulb is much the same brightness as a 100W tungsten lamp and while it draws 1A at 12V, you don't have the additional 88W of heating to worry about!
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NOTE: I have not checked that 12W 12V LED bayonet bulbs actually exist...