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Additional connection to earth 411.4.2

Simon Mitchell

Hi,

Regulation 411.4.2 regarding TN systems now includes a recommendation to install an additional connection to earth using an earth electrode. There is no indication within the regs why you would or wouldn't fit one. The guidance on language on p18 of the regs equates "recommendation" to "should". Therefore we should install an earth electrode to all TN-S and TN-C-S systems.

I can't find any discussion on this when searching but it seems quite a big change to previous regs. Should we be installing earth rods as a standard?

Simon

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  • 0

    Wasn't this the one that started off as a precaution against a broken PEN conductor in the supply ... but the sort of values to Earth for say a 100A installation turned out to be rather impractical (even foundation earthing might struggle in some conditions). But on the basis that something is better than nothing, and might be effective if you didn't have too much switched on at the time, it partly remained as a mere recommendation.

       -  Andy.

  • 0 in reply to AJJewsbury

    Not really ... always been permitted for TN systems (TN-S as well as PME), and even back in the 17th Ed BS 7671:2008, the Regulation had the Note regarding additional connections between PE and Earth.:

    NOTE: The PE and PEN conductors may additionally be connected to Earth, such as at the point of entry into the building.

    Even if we are talking about PME, though, additional earthing at MET has been noted for quite some time also, e.g. Appendix 3 (Fig 5) of the 15th Edition.

    So, whilst foundation earthing has been explored in more recent drafts for public comment of BS 7671, there's nothing new in terms of the ability to provide additional Earth electrodes connected to PE or MET (noting the para and items (a) and (b) before NOTE 3 in 722.411.4.1) - but there are now cases, discussed by Chapter 82, that necessitate it.

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  • 0 in reply to AJJewsbury

    Not really ... always been permitted for TN systems (TN-S as well as PME), and even back in the 17th Ed BS 7671:2008, the Regulation had the Note regarding additional connections between PE and Earth.:

    NOTE: The PE and PEN conductors may additionally be connected to Earth, such as at the point of entry into the building.

    Even if we are talking about PME, though, additional earthing at MET has been noted for quite some time also, e.g. Appendix 3 (Fig 5) of the 15th Edition.

    So, whilst foundation earthing has been explored in more recent drafts for public comment of BS 7671, there's nothing new in terms of the ability to provide additional Earth electrodes connected to PE or MET (noting the para and items (a) and (b) before NOTE 3 in 722.411.4.1) - but there are now cases, discussed by Chapter 82, that necessitate it.

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