I haven't heard specifically of that one but, as I've been writing, 'unnecessarily' connecting metal things to earth can, in some situations, increase the risk of electric shock (whether fatal or not). One has to balance that risk against the risk of not connecting it to earth - and try to decide which of the risks one thinks is the greater.
So, how would you determine that?
How do you determine that it is not?
So, you just decide that it is not an extraneous-c-p and then ignore?
I would.
Would it not because it would have the same effect?
By observation and common sense, with further investigation in the (rare) cases in which observation leaves some uncertainty? If the bath is entirely within the room, it clearly cannot, itself, normally "introduce a potential" (any potential) into that room. If potentials are being introduced into the room, it must be something else introducing them (even if that something else is a soaking wet ground floor).
Sort-of, I suppose - just as you would probably decide that an incoming metal service pipe, coming from a 'well above ground' outside meter which was fed by a plastic, was not an extraneous-c-p that required bonding.
You seem to be overlooking what all this is about. The concern is about a degree of 'connection' between an exposed metal part and something (e.g. true earth) which might possibly be at a different potential from that of the equipotential zone (i.e. MET/PEB potential). Conductive paths (whether 1Ω, 1,665Ω or whatever) between exposed metal and something which is AT that MET/PEB potential are of no real consequence, which is why they don't qualify as extraneous-c-ps. I suppose things would be clearer if extraneous-c-ps were defined as parts which were "liable to introduce a potential different from the potential of the equipotential zone", or something like that.
A big difference. Whilst, as above, a path from the bath to the MET/PEB is of no concern (and does not make it an extraneous-c-p), a path from the bath through a waterlogged solid floor to truth earth (which possibly could be at a potential different from that of the equipotential zone) IS a concern, and could render the bath an extraneous-c-p. As I said, observation would identify those cases in which this was a possibility, such that some tests (or, better, treating it as if it definitely were an extraneous-c-p) would then be appropriate.
In the obvious way, I suppose, by measuring the resistance from it to the PEB - and I wouldn't regard a resistance anything like as high as 1,666Ω as representing an 'effective connection' - I would be looking for a very small number of ohms, at most. However, this is the opposite way around from what we are talking about. The finding of a (any, of your choice) particular resistance between a bit of metal and the PEB never means that the bit of metal is necessarily an extraneous-c-p.
In turn, I think what you may be missing is that, even when it is required, supplementary equipotential bonding is only required between the CPCs of circuits in the location and extraneous-c-ps. The question of whether or not something is an extraneous-c-p (i.e. whether it is "liable to introduce a potential, generally earth potential") is therefore crucial in determining whether it needs to have supplementary bonding (if conditions for omission are not satisfied).
Why - if it is not an extraneous-c-p? Consider what I said before ... you agreed that a totally floating metal bath (near-infinite resistance to MET/PEB/CPCs) did not require any bonding. You are seemingly saying that if I connected it to a nearby CPC through a 15kΩ resistor (or the equivalent in damp walls/ floors/ whatever), it would then need bonding - but what hazard (that requires bonding to mitigate) do you believe has been introduced by that 15kΩ connection to the CPOCs etc.? If you are a person concerned about bernard's "drop a live hairdryer into a bath full of water' scenario, you might want to earth it (and, reasonably, would not regard a 15kΩ connection to earth as being adequate earthing), but there still would not be a reason for supplementary bonding, would there?
Because it is causing the same hazard as an extraneous-c-p, therefore...
Surely it would because you have introduced a situation equivalent to a part which is an extraneous-c-p and would require bonding.
Excessive touch voltage in the event of a fault.
I would not.
In that scenario the 15kΩ would be removed to make it isolated but if it could not be then supplementary bonding should be added to equalise potential.
There would because R>50/Ia.
Not normally but if it had that impedance, it would, wouldn't it.
None - except that those items will not be poorly connected to the pipes.
I do agree with that but it is the hypothetical we are discussing.
What sort of fault (and where), and what 'touch voltage'? You are talking as if the bath is a Class I Electrical appliance whose exposed parts (exposed-c-ps) could become live as a result of a fault within the appliance. Were that the case, then it would have to be earthed. However, that is not the case.
The "correct procedure" requires that (if conditions for omission of SB are not satisfied) that SB be installed to connect together all exposed-c-ps and extraneous-c-ps in the room - not anything else. Hence, if the bath is not either (it's obviously not an exposed-c-p, and could only be an extraneous-c-p if it were "liable to introduce a potential {different from the potential of the MET}"), there is no requirement to SB it, even if conditions for omission of SB are not satisfied.
It might.
A "poor-but-not-poor-enough connection to bonded pipework" will never, per se, render something an extraneous-c-p (as defined).
I agree totally, and have never suggested otherwise....
Where I disagree with EFLI is in relation to his apparent belief that a "poor-but-not-poor-enough connection" (he says 1,677Ω to 23kΩ) between a part and the MET/PEB/CPCs/whatever automatically renders that part an extraneous-c-p, which therefore requires supplementary bonding (if conditions for omission are not satisfied). As I've said to him, he appears to be using a circular argument, since his criteria for deciding whether something is an extraneous-c-p appears to be based on one of the stated requirements for omission of supplementary bonding IF it is an extraneous-c-p.
Yep, true. I should have written "... unless it is, or may become, connected to ...", or something like that. However, you know that's what I meant, and it doesn't alter anything else I've written.
Neither of those responses make sense to me. As I said, although not explicitly stated in the definition of an extraneous-c-p, it is clear that what matters is liability to "introduce a potential" which differs from that of the equipotential zone (MET, CPCs, bonded pipework etc.). 'Introducing' a potential into the equipotential zone which is the same as the potential of the equipotential zone is clearly of no consequence. In order for me to be able to comment further, I think you need to explain your responses above in a bit more detail!
Are you suggesting that everything with an electrical connection ('good', 'bad' or 'indifferent') to a (main bonded) extraneous-c-p thereby becomes an extraneous-c-p itself? If so, there will be an awful lot of extraneous-c-ps in the average building! If it becomes an extraneous-c-p, what is the "potential it is liable to introduce" (other than the potential of the MET/PEB/CPCs etc., which is hardly a problem!).
If it were an extraneous-c-p it would require 'main bonding'. What is your understanding of the reason for (function of) 'main bonding'?
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