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SWA Cable Above ground and earthing the armour

sparkiemike
When using SWA cable underground I always earth the armour, regardless of whether the armour is used as the cpc or not. The armour does provide some mechanical protection and it is important that the armour is earthed so that if the cable were penetrated (e.g. by a garden fork), the supply would automatically be disconnected by the protective device under this fault condition.
I have a situation on an existing domestic installation where I will be changing the consumer unit.  The 3-core SWA cable to the hot-tub rotary isolator is above ground and clipped to an outside wall.
The cable has not been terminated with brass glands, and at the ends the armour have been taped up, so no exposed conductive parts. The armour is not being used as the cpc.
At the rotary isolator for the hot-tub, stuffing glands have been used. The cable feeding the hot-tub does rest on the ground for about 1m before going into the hot-tub enclosure.
The earthing arrangement is TNCS, however at the hot-tub rotary isolator, the TNCS earth is not exported and there is an earth electrode for  the hot-tub’s cpc
Would you expect the armour to be earthed? Is it acceptable to terminate SWA without brass glands?
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    Chris Pearson:

    I assume that there is insufficient armour to be able to attach it to a brass gland at the new CU. It is appropriate to terminate the armouring in a stuffing gland at the downstream end, but I cannot find a regulation which requires a surface-mounted SWA cable to be earthed at the upstream end.


    The only caveat is that if the outer sheath were damaged, the armour would become an exposed conductive part.




    We are back to the discussion about the fact that SWA has single insulated conductors surrounded by a plastic filler or plastic yarn with wire wrapped around them covered with a plastic sheath.


    Single insulated conductors inside metal containment, so the metal containment needs earthing just as metal trunking or conduit containing single insulated singles does.


    Andy 

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  • 0

    Chris Pearson:

    I assume that there is insufficient armour to be able to attach it to a brass gland at the new CU. It is appropriate to terminate the armouring in a stuffing gland at the downstream end, but I cannot find a regulation which requires a surface-mounted SWA cable to be earthed at the upstream end.


    The only caveat is that if the outer sheath were damaged, the armour would become an exposed conductive part.




    We are back to the discussion about the fact that SWA has single insulated conductors surrounded by a plastic filler or plastic yarn with wire wrapped around them covered with a plastic sheath.


    Single insulated conductors inside metal containment, so the metal containment needs earthing just as metal trunking or conduit containing single insulated singles does.


    Andy 

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