OP
Badged01
….. is not considering the situation where supplementary bonding is NOT REQUIRED because the impedance of the parts is low enough in itself to limit any touch voltage to the safe amount…….
I didn’t want to end up with a lengthy and boring to and fro thread but feel you are completely off course in your interpretation/understanding of the application and need for supplementary equipotential bonding. Nowhere can I find anything that states supp bonding is not required if the impedances are low enough to limit meet the touch voltage requirement.
Section 701 states additional protection in the form of supp bonding SHALL be established connecting protective conductors to accessible extraneous-conductive parts in the location. My interpretation is there has to be a physical connection to achieve this in the location and this is supported by the advice/pictures/drawings in GN8 and the ESC publications.
Change the word “insulation” for “bonding” in the definition of Supplementary in the BGB. This I believe gives a further intent as to application of supplementary. That is supp bonding is applied in addition to main bonding for fault protection. (“applied” I interpret as meaning a physical connection as with main bonding.)
If main bonding is fitted you will always get a reading in the bathroom to showing continuity and 90% of the time it will meet touch voltages (assuming continuity of metalwork). Hence a reading alone will not prove supplementary bonding is physically present. You need to see it to confirm its presence.
Once you can see supp bonding, if you have any doubt as to the “effectiveness” of that supp bonding then you can test as per 415.2 using said touch voltage equation. No where in the regulations can I see anything that suggests this test alone is a substitute for confirming sup bonding is present, just “effective”. Its application is purely as a test if not sure that the supp bonding is “effective” in providing additional protection. (i.e. you’ve seen it and now want to test to confirm compliance.)
Even to apply this equation in practice, for me you have to be able to physically disconnect an end of the sup bonding and test, because if you have any bonding elsewhere in the premises your results will be effected by parallel paths. So if sup bonding isn’t there in the first place you cant prove its effectiveness just by using the equation?
At the end of the day sup bonding is there as an additional fault protection method and if you cant confirm its presence (not effectiveness) by the good old mark one eye-ball then no testing to an equation will convince me it is, just hidden somewhere. Lack of sup bonding can have serious implications in a fault situation should for example main bonding be lost, hence why the ESC consider lack of its presence being a C2 without an RCD fitted??
If there is anything in the regulations that Ive missed or goes against anything Ive stated then please advise and correct me. I am always learning and seeking new knowledge and understanding.
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