Hi I am installing a set of 3 low voltage halogen lights in my kitchen ceiling, however I find that the lead between light 1 and 2 is too short for my purpose.
I have read that the wiring rating on this side of the transformer needs to be substantial especially if its any length.
What gauge wire do I need to extend it to two metres?
Thanks Roger
A 1 mm csa' (cross sectional area) is enough for a 2 mtr length.
Would 1mm T+E be enough for several metres?
Replace 'spam' with 'org' to reply
Taking 1mm csa' for low voltage is good for anything up to 10 mtrs really. It's the low voltage part that makes the need for larger cross sectional area on the cable a necessity.
Actually, its the high current that "makes the need for larger cross sectional area..." but I know what you mean
- low voltage devices require a correspondingly high current to deliver the same wattage load so the amount of copper in the cable has to be higher the lower the voltage but the insulation can be thinner. (Follow that??) :-)
According to , for 3 at 12v 50W Halogens, you will need 2.5mm CSA twin to deliver the
150W at 12V over only 2m and will lose 0.5V along the cable, meaning you only have 11.5v at the fitting. For 10m, you'd need 16mm cable(!) Don't forget that 150w needs 12.5A at 12V , all assuming a resistive load.
IOW if the lights are very far apart you're better using more lower-power transformers near the lights than one xfmr and long cable runs.
John, I must thank you for this. I meant to type 10 mm csa' for this loading up to a length of 10 mtrs, and twice I have typed 1 mm csa'. I'm slowly cracking up here. The little yellow van is waiting around the bend for me. :-) Thanks again for updating and clarifying the details in my replies.
What, 10mm2 for a lighting circuit. Surely you are not serious.
Like the other poster said, more transformers is the way to go.
But that does beg the question of why to step down to 12V when there are 240V halgen bulbs available.
Anyone know why?
Replace 'spam' with 'org' to reply
Low voltage is considered safer from the POV of electrocution. Obviously it can be a fire hazard if the wiring is not up to spec, so it's six of one dozen/2 of the other.
No problem :-) I know it's that time of year one shouldn't be doing rewiring...
I used normal ring mains T & E
Actually its both. 1v loss on 250v is not as serious as 1v loss on 12v
and you get a lot more cable drop on a 5A LV 60W bulb than on a 0.25A mains one.
Could be for big power.
Depends. On thin celings with alnmostr no voids, cable in thnner than trensformers...
because they are 3 times as expensive and blow 10 times as quickly?
Yep, fraid so. As you lower the voltage you have to raise the current to deliver the same wattage. You should see some of the wiring I've had to do in my boat... it felt like I needed a pipe bender.
It's to do with the filament. As you increase the voltage you have to make the filament thinner and longer to increase its resistance to limit the current to the value necessary for the desired power output of the lamp (watts = volts x amps). If you want a small lamp, then you can't get enough wire inside the glass to get a sufficiently high resistance in a wire that is mechanically sound at the high temperature. Look at the supports needed in an ordinary lamp.
With Halogen lamps there is also an electrochemical reaction to take into account where there is a equilibrium temperature for the evaporation of the tungsten of the filament into the halide gas and vice- versa. At mains voltage, it is out of balance so they don't last as long. AFAICR, ~12v is the ideal voltage for the reaction versus element size in small fittings. (or summat like that- it's getting late)
I don't know the technical reasons, but from experience of having both types of halogen lighting in our new kitchen, I'd say the 12v ones have a much nicer quality of light.
12v ones produce a whiter, crisper light that creates those nice twinkles on reflective objects. They create a more modern feel to the room. The 240v ones give a more yellow light, similar to plain tungsten bulbs. I'm not so keen and would change them for 12v ones if it wasn't so much hassle.
I like the idea of mains and low voltage wires being instantly distinguishable. This must be safer than the other way round, but even so...
Cheaper solution is to wire the lights in series and use a higher voltage transformer from Maplins. But bear in mind this is a real pain when one light blows and they all go out.
If only it was just 10 times as quickly. Anybody want to buy some GU10 ceiling lights ?
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