Whilst I agree with most of what you wrote to Bernard, I think some may be confused by this statement - and I'm not totally sure what you meant to say. Do you perhaps mean 'if fault conditions arise, the RCD will (ignoring vanishingly improbable coincidences) clear the fault before anyone comes into contact with earthed/bonded metalwork'?
Yes, that was the 'vanishingly improbable coincidence' to which I referred. If an L-E fault 'occurred elsewhere', an RCD should clear it within a fraction of a second. For someone to be touching the pipe (or whatever) during that fraction of a second would be extrordinarily unlikely. In the absence of that amazing coincidence, an RCD would clear the fault before anyone touched the pipe (or whatever).
If a fault of Live to "earthed" metal work occurs then the RCD will operate.
Of course - but, in context, I think you're probably missing the point that, even if some people don't like the language, the regs only allow ommission of supplementary bonding in a bathroom if the extraneous-conductive-parts (pipes etc.) therein are effectively 'earthed'. Specifically, the regs require that the extraneous-conductive-parts' are "effectively connected" (usually via the pipework itself) to the main protective equipotential bonding - which, of course, is connected to the MET.
Of course they can, but they are vanishingly improbable! - and that certainly applies to what was being suggested.
That is true but you have admitted that it is a vanishingly improbable coincidence.
I'm sorry to stir things up again by making a distinction, but, if there are no exposed-conductive-parts it depends to some extent on whether you are talking about bonding, per se, or 'earthed bonding' (the latter being what the regs required). True 'simple bonding' which just connected together every bit of touchable metal in a bathroom would obviously protect a person from any shock provided that (if there were 'accidental' connections to earth, which would often be present via pipework) no new element (e.g. a vaccum cleaner, plugged in outside the room) were introduced into the bathroom. Even doing as the regs want, and 'earthing' that bonding ('bonding the CPCs, if you prefer') really shouldn't present any hazard (regardless of the potential of the CPC above true earth) if all metal in the room is bonded together - again, provided no-one introduces something new into the room.
Indeed - but when you say or imply that (in the absence of exposed-c-ps) supplementary bonding could actually decrease safety, that's only because of the (required by regs) extension of the bonding to the CPCs (which I would call 'earthing'if there are no exposed-c-ps), not because of the actual bonding of metalwork, per se.
Indeed. I suppose some would argue that, in situations in which supplementary is not required by the regs, one could just bond the extraneous-c-ps together without having to extend the bonding to include CPCs - but I really don't see what would be the point.
Glad you agree!
Well, yes. There probably is just about an argument. The row of clamps joined by G/Y in the airing cupboard, and maybe also in the vicinity of the boiler, 'bonding everything together' (but not necessarily to CPCs) is the traditional way of achieving that. The reality, of course, is that the chances of there ever being a significant PD between such pipes is extremely small, particularly given that if 'anything electrical' is involved with any of them there will be a connection to the CPC, and that (given metal plumbing) some/most/all will be in contunuity with main bonding connections.
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