SWA earth termination....help settle an argument!!

18 Jun 2009
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United Kingdom
Hello All,

Can you help confirm something for me....

I have advised a mate (I am not in the trade .....well electronics actually and they know it!) that when terminating SWA cable you MUST take the protective armoured earth on a dedicated conductor from a Universal Box using a Banjo to the CU.

You are not allowed to link up the Armour earth from the Banjo to the Earth core of the Cable inside the Universal Box, and then take the single Cable Earth to the CU.

Am I correct?
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IMO, no, thats not correct in this situation.

If the swa was being used functionally as the cpc/main bonding that might be different.

However, in this instance, as you are already using a core as earth, you are simply connecting the swa to earth as an ECP.
There are no rules as you refer to. But of course the cable must be effectively earthed and there are rules about size of earth cable when.
1) Not part of a multi-core cable.
2) Used as a main protective bonding conductor
3) Used as a supplementary protective bonding conductor
It is possible because of these rules that in some cases the earth cable in for example a twin and earth cable would be under size where the SWA would not and there may be cases where it is required to use separate earth cables.
Chapter 54 is 8 pages long and covers the size of earth cables.

Thanks...so I may be correct!!!....but...

Apparently the application is with 6mm 3core SWA going from a Garage into an external Universal box and from there into a Consumer unit, so the external armour is not being used as primary earth.

He already has 3core 6mm at the box to the consumer unit and does not want to replace it with 4 core and have a 'dedicated' armour earth to the CU......too lazy :)
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