Fair enough - so what has got something 'to do with it'?
Twin + Earth - no sleeve on earth
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I do like to ask ChatGPT for an opinion, when these sort of questions appear! 
...after an hour of patent trawling, could we be getting closer to an answer?!
If one of the original intentions of the design was to have the middle earth conductor as a 'rip cord', would an unsheathed conductor work better?
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If one of the original intentions of the design was to have the middle earth conductor as a 'rip cord', would an unsheathed conductor work better?
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Good for youI do like to ask ChatGPT for an opinion, when these sort of questions appear!
I presume that explanation must 'come fromsomewhere' -so I wonder 'where?'. If I were an electrician (and even given that I am not), I'm not sure I would be too impressed by the suggestion that I needed the CPC to be bare in order to identify it as such!
Kind Regards, John
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It's really just a description, rather than an 'explanation'. It does mention 'rip cord' but doesn't actually say that the CPC fulfils that function....after an hour of patent trawling, could we be getting closer to an answer?!
I think so. I have to confess that I not infrequently use that method of 'stripping', and the CPC 'works' much better than do the insulated conductors. That seems to make intuitive sense, since the bare copper is much smaller (hence higher pressure on sheath for given force applied to it, and does not have a somewhat 'squashy' covering. A 'cheese wire' undoubtedly cuts cheese much more easily than it would if covered in a substantial plastic coating.
Kind Regards, John
Presumably the not infrequent failure of idiots and vagabonds to sleeve the protective conductor, even though required by the Wiring Rules. Also presumably to increase harmonisation with cables for similar purposes in other jurisdictions.
Do I take it that those Wiring Regulations explicitly relate to the sleeving of bare conductors, as well as the 'over-sleeving' of insulated ones? The later, of course, would only be undertaken as a means of identification, which isn't really required in the case of a bare CPC conductor.
As for your reference to "idiots and vagabonds" you will be aware, that BS7671 does not explicitly require bare CPCs to be sleeved, and some people argue that it is not necessary
Maybe, but one might expect them to want harmonisation with the closest of those 'other jurisdictions'.
Kind Regards, John
ChatGPT was trained on a dataset of around 600GB of text information.
60% of the data came from 8 years of web crawling, 22% from (basically) 'upvoted' Reddit posts!, 16% from two online book repositories and 3% came from (the whole of) the English language version of Wikipedia.
Although the answer to a question may be incorrect, ChatGPT gives a sort of 'averaged' answer based on the general consensus of responses within its dataset.
ChatGPT can, however, be overconfident in its answers, and occasionally make answers up!
Unfortunately, we have no idea of the weightings it gives to certain information - i.e. how many mentions of "unsheathed CPC in twin and earth" can there be on the internet? - if there were only one explicit and confident mention on a Reddit post, this may be the answer ChatGPT gives out as a fact.
Probably not, but you can't argue with the internet!
Perhaps that wasn't the best quote to pull out, but it is mentioned elsewhere in the link, that the middle conductor is used as the rip cord and this is assumed to be the earth conductor. I.e.
I have never liked using the cpc as a ripcord, abuse of the earthwire.
Tin hat on head, ducking under the parapet
Tin hat on head, ducking under the parapet
But it appears from the patent that the cpc was specifically intended to serve as a ripcord, so it should be able to withstand that (ab)use.I have never liked using the cpc as a ripcord, abuse of the earthwire.
Tin hat on head, ducking under the parapet
I don't care why it's not already covered but it just wish is was as I hate the fiddlyness of putting sleeving on...
Yes, I understand that, but if the "sort-of-averaged" answer was such as it produced, the some of its source must have said something similar, so I was wondering what those sources might be. We won't ever know, unless someone finds some individual sources saying a similar thing.
Hmmm. I'm not sure which "you" was in your mind but I can (not not infrequently do) 'argue with the internetProbably not, but you can't argue with the internet!
Kind Regards, John
I suppose you are very probably right about the intention/implication, the actual wording is not particularly clear/explicit in eitehr of the passages you have quoted, namely ...
.... and ....
n your first quote, and ..
...in your second quoted section. Although perhaps implied, neither actually say that the CPC is used for the 'ripping'.
Interestingly, whilst the first of your quotes used the words "cable" and "conductor" in a manner that would be regarded as 'correct' today, this second one refers to the bare CPC as "the earth cable" ["or rip cord"].
Kind Regards, John
As I implied, I've quite often done it (and still do), but always feel a little 'guilty', and probably mentally check that no-one is looking over my shoulderI have never liked using the cpc as a ripcord, abuse of the earthwire. Tin hat on head, ducking under the parapet
Having said that, in the fairly distant past I did attempt to ascertain how much 'damage' I might be doing, and came to the conclusion that any resultant stretching of the CPC (henc potential reduction in CPC, and potential changes in mechanical properties) was virtually imperceptible - so I felt fairly reassured.
I would add that my reason for taking that approach has not been primarily a matter of 'laziness' but, rather, that any other approaches involve the use of a knife/blade/whatever that might damage the insulation of the live conductors. I have therefore tended to regard the 'ripping' approach as probably, 'on balance', being 'safer'
I would add that if/when one does do it, then it is advisable to first make a small 'nick' in the sheathing (for the 'rip cord' to use as a starting point), because if one tries to 'start the rip' with the CPC, one sometimes has to pull so hard that stretching, or even fracture, of the CPC is a possibility.
Kind Regards, John
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