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Split concentric ccc?

Farmboy

Hi all



Basically, what ccc table, if any, in apdx 4 would be used for split concentric? I've had a look on the old forum but couldn't see a definitive answer, so sorry if I've just missed it.



The scenario is an existing domestic installation has an approx 7 metre run of what appears to be 25mm2 cable running from the external meter box, under the floor, to the internal CU, on a 100A main fuse, with no switch fuse.



The installation method is awkward to determine because the cable comes up internally through the floor screed, making it seem to be buried under the concrete floor. However, there also appears to be an approx rough/faint 100mm circular pattern around the cable which makes me think there may be a duct (probably brown plastic drainage pipe) just below the surface, but can't be sure, could just be the way the screed was smoothed around the cable.



So, if there's a duct, will that satisfy reg 522.8.10 (probably no cable making though), so the concentric can remain? But if there's no duct, should it be disused/replaced because the cables protective earth only surrounds 1/3 of the cable?



So if the cable can remain, what ccc and size of switch fuse?



Thoughts please - apart from run the other way ?


F


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  • 0

    davezawadi:

    I agree Alan, but that does not make an existing installation "dangerous", but simply non-compliant. . . 




    I agree. I was pointing out the shortcomings of split concentric, as not everyone will realise that the neutral isn’t insulated to the same extent as the phase. 

     



    . . . I presume the DNO connected these tails to the meter . . . 



    We have to. In connecting them, the meter supplier / DNO is deemed to have accepted them. 


    As a correction to my post above which the new forum software prevents me from editing, the neutral of course covers two thirds of the diameter, the earth the remaining third. 


    Regards,


    Alan. 

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  • 0

    davezawadi:

    I agree Alan, but that does not make an existing installation "dangerous", but simply non-compliant. . . 




    I agree. I was pointing out the shortcomings of split concentric, as not everyone will realise that the neutral isn’t insulated to the same extent as the phase. 

     



    . . . I presume the DNO connected these tails to the meter . . . 



    We have to. In connecting them, the meter supplier / DNO is deemed to have accepted them. 


    As a correction to my post above which the new forum software prevents me from editing, the neutral of course covers two thirds of the diameter, the earth the remaining third. 


    Regards,


    Alan. 

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