Extra-low voltage house wiring

Can someone with access to AS3000 comment on the cabling requirements for Extra-low voltage runs in a domestic situation.

What I would like to do is run in an extra-low voltage (ie 12V nom) sub system to power lighting. I have no doubt this seems a little odd, but there is method to my madness. My question is around required labelling of such wiring. Given that there is mains wiring in the house already, I assume I would need to identify the extra-low voltage cabling to avoid this sub system being accidentally connected to the mains.
Dose the AS make any reference to this type of work?

Thanks

Have found a little more...
http://en.wikipedia.org/wiki/Extra-low_voltage

 

The only reference I can see about protection from a higher voltage is this:

So you will need to plug ELV devices in a unique plug to the rest of the installation. Where I work we used outlets and plugs with a rounded earth pin which only ELV plugs will fit in (which does not have an earth cable attached.)

Also LV and ELV cabling needs segregation (eg; fixed and continuous barriers between conductors)

 

Steveo is bang on the money.

You have the segregation requirement (100mm from memory, unless it is a hard barrier) and the plugs cannot be interchangeable. There is a 2-pin "T" socket which is pretty common in ELV installations.

 

Nice one,

Thank you gents.

 

Sooo, whats the method to the madness? f'loads of LED lighting??

 

Na nothing quite that cool, just a large AGM SLR and solar cell I used to have installed in the Land Rover. I've been keeping the battery topped up with the pannel (and reg of cause) since it came out of the car, thought I could make some use of the power to run a low voltage sensor light over the front steps. (hmmm and maybe run the modem router, and maybe... lol)

 

Separate to your query about the rules, you'd want reasonably heavy duty wire or to keep your wiring reasonably short. I believe you'd also have to have protective fusing on the solar panel and on the battery.

 

would not the modem router introduce possible higher voltage into the elv system via the phone line? (no sparky here just curious )

 

unlikely, its super low current anyway

 

There is an isolating transformer and insulation between the PSTN side of the modem and the ELV side of the modem - this is a requirement for it to be allowed to be connected to the telephone network.

 

System is already fused correctly, it has been running in my Landy for some time, only thing that will change is the connection (via an isolator) to the main battery.
Yes the "I squared R" losses will be a lot higher than they would be on mains for devices of a given power, but I don't intend running anything particularlly high powered on it anyway. (router is a couple of hundred mA, Led sensor lights about the same if I really go on with them.)
Having read the Wiki entry on it, I am thinking 4mm builders' cable in condute marked at each end and a note in the fuse box alerting to the presence of ELV wiring. Probably pull it out before selling up anyway.

 

always wondered about that. so there's no chance a big surge could jump from pstn to elv?

 

A common-mode surge (high voltage between the pair and ground) would need to exceed about 1.5kV to cross to the ELV side of the modem, while a differential-mode surge (high voltage between the wires in the pair) that'd damage the ADSL modem would also damage your phone.

 

i see. I spose thats why voltage let through can be so high ie 1000v on so many telephone surge suppression devices.

 

All PSTN devices are hardened and protected against that sort of thing, with gas suppressors as well as the isolating transformer.