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Concentric cable, consumer side.

JohnE

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?

Parents
  • 0

    So if you use semantics to make it comply, does that make it safe? 

  • 0 in reply to lyledunn
    lyledunn said:
    So if you use semantics to make it comply, does that make it safe? 

    I know the above is perhaps a divisive question ... and I do see the point ... but 'comply' with what exactly?

    In terms of ESQCR, all that needs to be established is whether the wiring is the responsibility of a Consumer or not. That might rest on where the meters are ... or not ... but without knowing a little more about the installation, this one's tricky.

    BS 7671 on the other hand does not prohibit PEN conductors. It does, however, prohibit re-combining N and PE after you've split them. So, we'd have to establish whether that has happened before saying it doesn't conform to BS 7671 ?

    So, I don't think it's so much 'semantics' I was playing with, but trying to get an understanding of the arrangement to see if we could establish a better-informed opinion ?

  • 0 in reply to gkenyon

    It's safer than T and E sub-mains that would probably be a "C3"- the live is surrounded by neutral, and as neutral is within  a volt or two of earth in a TNCS system, it is almost as safe as a correctly earthed SWA - we need two faults, the mis placed nail and an open circuit neutral to make it immediately dangerous.
    SWA is very similar.

    What we are doing is choosing the right bit of the right regs to apply, to recognize that level of safety.

    More generally:-
    Complying with all or any regs is not on its own a guarantee of safety in all cases - some sense is required.

    Non-compliance is not a guarantee of danger, but needs more thought before deciding if something is OK or not.

    in short, BS7671 is neither always sufficient, nor always necessary..... but in most cases of course it is ;-)
    Mike.

  • 0 in reply to lyledunn

    I would argue that it was safe anyway, but that careful use of semantics could perhaps be justified as a way to prove that safety.

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