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
