Solid Core Earth in multicore

yowie7860 · Jul 31, 2023

So, according to AS 3000

5.3.2 Earthing conductor material and type 5.3.2.1 Conductor material 5.3.2.1.1 Copper conductors Copper earthing conductors shall be of high conductivity copper and shall be in the form of— (a) stranded conductors; (b) circular braided conductors; or (c) solid conductors having a cross-sectional area not less than 10 mm2 and a thickness not less than 1.5 mm. Exceptions: 1 A smaller solid conductor may be used where permitted by a particular cable Standard.

Can anyone offer any advice on the Exception? what other cable standards are they referring to here?
We want to use some 2.5mm2 solid core earth as part of multi core cable that was imported. The cable meets all European standards, not some dodgy crap out of Bangkok.

Dustydazzler · Jul 31, 2023

Here in the UK we have a reduced sized CPC ( earth ) in our flat twin and earth cable Which I believe is fairly unique to our flat solid core cable as our flexible standed cable has all the same sized conductores.

When I started in the trade in the mid 1990s rumour amongst the older sparks was the small CPC was due to copper price and to keep cable price low. But the electrical theory suggests as the CPC should only carry a current / fault current for a few seconds it can be made smaller. Which in turn should keep a the price down as uses less copper to make a roll of flat cable

pc1966 · Jul 31, 2023

The reduced-size and unsheathed CPC for domestic fixed wiring is mostly a UK thing for those reasons (less copper cost, lighter cable, smaller bend radius, etc) and is fine so long as it meets the disconnection requirements.

The UK has long had a very strong emphasis on meeting ADS via a low enough Zs which helps, but also our fused 13A plugs mean that even pre-RCD you could never get that much non-tripping fault current even with a stupidly long extension lead, etc, that invalidates the fixed wiring Zs. E.g. the 1,5mm CPC in 2.5mm T&E, etc, can never carry the available current from a 13A fuse.

Not much help to the OP though!