Kiwi, As far as I'm aware, the red-sheathed 2-Core TPS cable has the same properties as it's white-sheathed brother, ie: has a 600V/1kV rating, the only difference being that it has a Red outer sheath to denote the system as a Fire Alarm system. Even so, it has a conductor size of either 1.0mm2 solid or 1.5mm2 stranded. As Ray rightfully mentions, it is contrary to the Regulations to install a cable in Domestic Installations without an integral Earth conductor. Having said that, I've worked in heaps of houses where the switch wire from the batten-holder to the light switch (in a 3-plated system) is only a 2-Core (Red/Black) cable. Also depends on when the place was wired originally.
Surely it must have been allowed to wire lighting circuits in the past with no integral earth. I've seen it a million times. Or was it a popular cost-cutting measure that went unnoticed by the inspector ?
Some people may have thought that wiring a domestic dwelling in red twin was okay as there was no fire alarm wiring anyway.
In the U.K., the IEE Regs. only required earths from 1966 onward. Prior to that, earths could be omitted on lighting circuits so long as certain conditions were met: No switches with exposed metalwork, any metal light fixtures to be mounted out of reach, etc.
That may be right Pauluk, as most of the twin lighting wire I'm finding now is from houses built in the 60's.
Has anyones regs ever stated that a metal light fitting doesn't have to be earthed if it is placed higher than a certain measurement above ground level ? I've heard that theory alot here and I've never been able to find anything in AS/NZS 3000. ( I can't be bothered looking in the old regs ).
If you're referring to AS/NZS 3000, there's nothing against wiring the circuits in twin with a separately run earth wire to each point.
No I'm not actually, before the AS/NZS thing and still, we have our own Regulations here, have you read them?. The fact that local Regulations are being watered down in favour of a "one size fits all" across countries, is just one of the reasons I'm happy with leaving this industry. AS/NZS 3000 is nothing more than a compromise, from both sides.
Each state has it's own electrical regulations. AS/NZS 3000 is simply a document and requires local legislation to make it enforceable. Why do you consider the wiring rules a compromise? What don't you like about it?