Low Voltage Lights

No it's not normally done that way. The switches may not be rated for enough current on the 12V side. The extra cable length to switch and back will drop precious volts. The transformer is presumably on all the time. Some electronic ones will shut down if there isn't enough load on them and not restart until the supply is interrupted.

Not the way I've seen them wired up.

I've always seen them wired with the switching on the 240v side, as you expected.

The low-voltage side has correspondingly higher currents. Why would anyone intentionally run these high currents through the additional wiring length to the switches, and also expose the switch contacts to high currents to interrupt?

Seems wrong to me.

Its not the best way to do it in most cases, though there will be exceptions where it is. Just saying dont assume it must be rewired, it might have worked fine that way, and continue to once the fault is fixed. OTOH it may be that the transformer min load is not being complied with, or the swiches are seeing above theur rated current.

NT

I'm struggling to think of any myself!

David

Oh... if both switches are underwater I'd say it was a good idea.. ;-)

Doing it this way and assuming 1mm cable, the cable will overload on 10 spots each drawing 1.6A (20w/12v) table 4D5A IEE regs

First I'd want to be sure it's a true 12 volts and not just some form of coupling.

But if it is, it's not a good idea. Excessive voltage drop on the cable and a permanently 'live' transformer. Also if more than 60 watts you're probably exceeding the load for the switches.

yeah especially with the cheap light switches only rated at 6A. The better ones are rated at 10A but still less than the cable itself.