I was only guessing!
ZIG ZAG UnSAFE zone
- Thread starter bernardgreen
- Start date
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In as much as a back box (as opposed to a bare CPC 'almost touching' a live terminal) is unlikley to move, I would think the answer to that would be 'no'.
In fact, some of the arguments we've seen could be taken to silly extremes. If, as seems to be the case, the concern is that, in the event of an L-CPC fault, parts or all of the CPC system would become live for a very brief period of time before a protective device operated, we would perhaps have to rethink the whole idea of having exposed-c-ps 'earthed'. However, I would imagine that most of us would much prefer them to be earthed, so that the device hopefully would operate very quickly, than to not have them earthed!
Kind Regards, John
Oh I thought he was talking about me
About four posts before yours, I wrote:
You then went on to point out, not unreasonably, that even if there were no such bang, but the bare CPC was very close to an L terminal, it was possible that dust or moisture (or maybe movement?) might result in an L-CPC path emerging.
Kind Regards, John
I must admit I missed John's reply - sorry - so two replies giving the same reason.
No one seems to have said that if terminated correctly the CPC should not be able to touch the Line copper.
No one seems to have said that if terminated correctly the CPC should not be able to touch the Line copper.
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I wouldn't regard myself as a "very casual electrical DIYer who lacked dexterity" either, and I can certainly remember tightening down an earth terminal and then when giving the customary little pull on the conductor to check realizing that the end of the sleeving was caught in the terminal. In fact when working in some awkward positions with certain types of terminals it's happened enough times that, at least for me, that customary little pull after tightening is not just to check that the conductor is gripped securely in the terminal but for the earths also to check that the sleeving is not caught!
Not something I have to worry about now.........
If the 'risk' has been 'identified' on the basis of 'what is theoretically possible' (rather than evidence that it ever actually happens), one has to decide whether it is a 'significant' risk before taking any action. Either you are I could come up with contrived 'theoretically possible' events (probably combinations of events), the likelihood of which was so incredibly small that it would be ludicrous to even think about measures to reduce the (already very near zero) risk.
I have agreed that the particular issue is trivial. My concern is that the same argument could be applied to situations in which the cost of 'measures to reduce a (possibly negligible) risk' would be far from trivial
In any event, IF you believe that RCDs are desirable ('save lives') and IF you believe that the in-service failure rates of RCDs is at least 1% or so (rather than the oft-quoted 7% or 1 in 7 {I can never remember which!}) then presumably you would feel that there was duty to do something about that 'identified risk' (presumably potentially much greater than that of unsleeeved CPCs), such as demanding at least two RCDs. However, if the failure rate is finite, then you could 'identify the (non-zero) risk' of two RCDs both failing, so (despitre the very low risk) would you then have a duty to demand tree .....??!!
Whether you like it or not, it is necessary to make decisions based on whether or not the magnitude of a risk is regarded as high enough 'to warrant any action'.
Kind Regards, John
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Indeed, if the argument is that the earth conductor needs to be sleeved to guard against the remote possibility of this happening, then surely the same should apply to every other piece of exposed earthed metalwork contained within the box, as well as the box itself, if metallic?
How about the bare metal strap which is often found linking the two earth terminals on opposite sides of a double socket? Or the earth terminal itself, which is often exposed?
No problem!
I'm not sure what you're suggesting. I would say the L and E terminals on some accessories are so close that it would be almost impossible to 'terminate the CPC correctly' such that there was no risk of a bare CPC coming into contact with (or coming very close to) the L terminal when everything was pushed back into the back box, aren't they?
Kind Regards, John
The only significance of identifying a risk as 'significant' is that that is the threshold for documenting said risk.
I don't believe that the in-service failure rate of RCDs from reputable manufacturers is anywhere near 1%, and the cost of providing duplicated RCDs, which would have to be of different types to avoid common-cause failures, would not be insignificant.
Whether you like it or not, there are clear duties laid down in, for example, the Health & Safety at Work Act.
And even with sleeving, could you guarantee absolutely no risk of the sleeving being pushed back and still allowing contact if things are that tight? Perhaps it's a consequence of the prevalence of masonry construction and the difficulty of cutting out for deeper boxes, but I often used to feel that the boxes typically used in British wiring are, shall we say, not exactly generous in depth.
Which is totally irrelevant to somebody working on his own home.
I was just thinking people meant an exposed bit of line conductor; you mean the CPC is going to contact the actual terminal.
Fair enough.
That could be the real reason then. Make everyone sleeve CPC instead of forcing manufacturers to construct safer accessories.
On the other hand, if the CPC would have caused a short but for a bit of sleeving it may not be ideal.
Fair enough.
That could be the real reason then. Make everyone sleeve CPC instead of forcing manufacturers to construct safer accessories.
On the other hand, if the CPC would have caused a short but for a bit of sleeving it may not be ideal.
Exactly my point. One has to have at least some estimate (even if only a 'guesstimate') of the magnitude of a risk ('quantification') in order to know whether it warrants any attention/action (or whether it creates any duty to reduce the risk).
Sure - but, as above, presumably only in relation to risks regarded as 'significant' (in magnitude)?
Kind Regards, John
I can't speak for 'people' but, no, as far as I am concerned, I was assuming that the L conductor was fully insulated, the problem relating to the totally bare length of CPC (if not sleeved) which could 'bend anywhere' when one pushes everything into the box!
As above, I think that with some accessories there is always going to be some (small) risk that, in the absence of sleeving, the CPC could come in contact with an L terminal.
Kind Regards, John
No, there's a duty (for professionals) to reduce all risks as low as reasonably practicable, and to document the significant risks and the actions taken to reduce them.
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