Low Voltage Cabling Query (Dimmer then transformer?)

You might need bigger cable for the LV runs, particularly if they're more than a metre or two. This is because to have the same power at a lower voltage, you need to increase the current. The increased current leads to greater voltage drop. As you have only 12V to start with, this increased voltage drop has much greater significance than it would have with mains voltage.

Christian.

The dimmers connect in the mains *input* circuit to the transformers - *not* on the 12v side.

As Christian has said, you may need heavier cable on the LV side. It depends on the distance of the lamps from the transformer and whether you're wiring them in a multi-drop or star arrangement. If you're using a star, and the cables are short, 1.5mm^2 cable is ok. Otherwise, use 2.5mm^2. Leave the earth disconnected on *both* sides of the transformers.

Good luck with your dimming! I ended up abandoning dimming because I got a horrible buzzing noise out of the transformers - even at full power and even though I was using dimmers and transformers which claimed to be compatible with each other! As a backup, plan to have several groups of lights, with each group being separately switched so that you can vary the overall light intensity by selective switching.

On Thu, 08 Apr 2004 13:08:07 GMT, in uk.d-i-y "Seri" strung together this:

This one.

Technically 1.5 will manage up to around 3m, 2.5 up to around 5-6m, although I've always used 1\1.5mm for low voltage wiring and never had any problems

Thanks folks, all now fitted and working.

Have to say for the benefit of 'Set Square' if he should try again one day: Varilux Dimmable Transformers

Now it looks like my next job is going to be ripping out the fibre-glass insulation I discovered we had whilst fitting the things, I itch all over at the moment.

Thanks for all your help on the group, it was, as always, accurate and extremely appreciated.

Seri

| >My question is, should the order be: | >Consumer Unit -> Dimmer Switch -> Transformer -> Bulbs | | This one. | >

| >also, I'm presuming that standard 1.5mm T&E lighting cable is fine to be | >used and I simply leave the earth loose when connecting each spot to it. | | Technically 1.5 will manage up to around 3m, 2.5 up to around 5-6m, | although I've always used 1\1.5mm for low voltage wiring and never had | any problems | -- | | SJW | A.C.S. Ltd.

If it's going to be a while before you get around to ripping it all out, please make sure that it isn't covering the transformers and light fittings! They need some ventillation. It may also be worthwhile making sure that the LV-side cables aren't covered.

Hwyl!

M.