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Separate main bonding to outbuilding

Former Community Member
Former Community Member
Hi, I just wanted people’s thoughts on this please.

I have been to a job with a TN-S supply. A sub main feeds a separate building with an SWA, the armour being used as the CPC. I have calculated the armour has not the additional cross sectional area to used as the required main bonding. I understand from GN8 that the main bonding needs to be extended to the building as specified in size by BS7671. I realise that this main bond will run from the MET to the Earth marshalling terminal in the second building. My question is this:

The SWA is buried and cannot be dug up (well easily). There is a second duct that runs between the buildings which is empty, but it follows a different route to the SWA. I seem to remember reading that it is best to run a separate bonding cable in close proximity to the existing SWA, am I correct or did I dream this? Is it advisable not to run the additional cable via a different route? If so, my only option will be to TT the second building.


Thanks in advance.


KS
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    AJJewsbury:
    Besides which he paid a lot of money to get the HV line and Tx moved out of view,

    Presumably he wasn't the only consumer on that Tx then - otherwise it might have been PNB rather than PME - then table 54.8 could have been neatly side-stepped.

       - Andy.


    Where PNB is provided from an LV public distribution system, then, unless it's declared as TN-S (some flavours of PNB from some distributors are), then PME conditions apply - see G12/4


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  • 0
    AJJewsbury:
    Besides which he paid a lot of money to get the HV line and Tx moved out of view,

    Presumably he wasn't the only consumer on that Tx then - otherwise it might have been PNB rather than PME - then table 54.8 could have been neatly side-stepped.

       - Andy.


    Where PNB is provided from an LV public distribution system, then, unless it's declared as TN-S (some flavours of PNB from some distributors are), then PME conditions apply - see G12/4


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