Concentric cable, consumer side.

Question

A house converted into three flats probably 20+ years ago. TNCS supply. Earthing conductor onto the MET Meter tails in to three 60A switch fuses Concentric cable ran from the switch fuses to the three flats consumer units. Solid Aluminium core. Decent size must be 25mm multi stranded copper neutral , haven't counted but lots. Separate 16mm earth ran to each flat from the DNO labeled MET. 
 Replacing the board in one of the flats. 
 My concerns Cable ran in the fabric of the building, No earthed protection, No RCD protection, Tails not double insulated, dissimilar metals But.. Cable all as clean as the day it went in, aluminium clean and bright, better than twin and earth, which has been pointed out on other searches. 
 
 Is this OK for continued use?

mapj1 · Accepted Answer

Well, it is clearly a non compliance against current regs. It may well have been allowed when it went in,though - for quite a while concentric cables were permitted. 
 Is it a dangerous non-compliance ? probably not, especially if the cable route is either obvious or mostly in the 'landlords area' where random tenants should not be hanging pictures anyway. And in practice assuming neutral is the outer, then any nail accidents will result in power going off smartly. We'd not worry if it was a network operator's cable after all. 
 If it is too accessible at the ends where it is single insulated, can things be sleeved or 'wizards hatted' or protected with mini-trunking or similar ? 
 Mike.

statter · Answer

I agree. One point to watch though if you are replacing whatever is on the end is that the terminal that receives the solid Al core needs to have been designed with that in mind. I dont have the standards to hand but I would definately check before terminating it in anything different to the original. DNO terminals for this sort of thing are mostly relatively heavy copper blocks with multiple screws which are tightened to required torque. I doubt that you would get a decent connection with any longevity with a cage type terminal.

Concentric cable, consumer side.

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