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Earthing/Bonding advise please

D4G
Hi all, i'm after some advise and thought this would be the best place to ask ?


I have a supply cable to an out building, currently in 16mm T&E and an underground copper water supply also in the out building.  The pipe currently has no bonding.

I want to upgrade the cable to the out building.  Would a 16mm 3 core SWA be suitable, using the 3rd core as a combined CPC and bonding conductor.


Main supply to house is overhead assumed to be TNS due to the supply cable being Split Concentric....



Thanks in advance
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  • 0

    Is it common to find unbonded extraneous conductors?



    Maybe not common these days, but certainly far from unknown.

     

    Another question, what size should the links be from the SWA glands to the earth terminal?



    Slightly tricky that - if you want to avoid any nasty calculations about how any fault current is going to divide between the PE core and the armour, the simplest thing is to assume the same size as the whole of the minimum required for its various functions - as a c.p.c. you can either calculate it (based on worst combination of Zs, the protective device and  material) or size it the same as the line conductor, as bonding conductor it would have to be at least 10mm². In that it's a 16mm² cable and crimping on a 16mm² lug isn't any harder than a 10mm² one and you'll probably have a 16mm² offcut I'd probably just do it in 16mm² and have done with it.


      - Andy.
Reply
  • 0

    Is it common to find unbonded extraneous conductors?



    Maybe not common these days, but certainly far from unknown.

     

    Another question, what size should the links be from the SWA glands to the earth terminal?



    Slightly tricky that - if you want to avoid any nasty calculations about how any fault current is going to divide between the PE core and the armour, the simplest thing is to assume the same size as the whole of the minimum required for its various functions - as a c.p.c. you can either calculate it (based on worst combination of Zs, the protective device and  material) or size it the same as the line conductor, as bonding conductor it would have to be at least 10mm². In that it's a 16mm² cable and crimping on a 16mm² lug isn't any harder than a 10mm² one and you'll probably have a 16mm² offcut I'd probably just do it in 16mm² and have done with it.


      - Andy.
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