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practical need for supp bonding in bathroom

wallywombat
Can anyone suggest a realistic scenario where supplementary bonding would be required in a bathroom or other 701 location? I'm failing to think of one, although I may be overlooking something blindingly obvious.


It can be omitted as long all three of these are satisfied: ADS in time; RCD present; any extr-c-p connected to main bonding.


If ADS can't be done in time by either MCB/RCD then its not legal anyway.

RCD has to be present anyway.

Water and gas pipes etc should already be main bonded if they introduce a potential.
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  • 0
    " Before we get too hung up about existing installations, let's consider just a new build to 18th Ed. Is there a scenario which is fully 18th compliant and which requires supp bonding? "

    yes for an 18th edition  rewire in an building of unknown vintage.

    The effectiveness of the connection of extraneous-conductive-parts in the location to the main earthing terminal may

    be assessed, where necessary, by the appication of Regulation 415.2.2.




    and then




    415.2.2 The resistance R between simultaneously accessible exposed-conductive-parts and extraneous conductive parts shall fulfil the following condition:

    R <50 V/Ia in AC systems... where Ia is the operating current in amperes (A) of the protective device or:

    (i) for RCDs, Ian

    (ii) for overcurrent devices, the 5 s operating current.






    Not unknown for items like a cast iron soil stack, or existing metal radiators, to be not really as well bonded back to the MET as this requires, and at the same time not well enough isolated from ground to be truly considered not to be an extraneous part.

    In such a case a local bond solves the issue.

     


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  • 0
    " Before we get too hung up about existing installations, let's consider just a new build to 18th Ed. Is there a scenario which is fully 18th compliant and which requires supp bonding? "

    yes for an 18th edition  rewire in an building of unknown vintage.

    The effectiveness of the connection of extraneous-conductive-parts in the location to the main earthing terminal may

    be assessed, where necessary, by the appication of Regulation 415.2.2.




    and then




    415.2.2 The resistance R between simultaneously accessible exposed-conductive-parts and extraneous conductive parts shall fulfil the following condition:

    R <50 V/Ia in AC systems... where Ia is the operating current in amperes (A) of the protective device or:

    (i) for RCDs, Ian

    (ii) for overcurrent devices, the 5 s operating current.






    Not unknown for items like a cast iron soil stack, or existing metal radiators, to be not really as well bonded back to the MET as this requires, and at the same time not well enough isolated from ground to be truly considered not to be an extraneous part.

    In such a case a local bond solves the issue.

     


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