Do you really think that one would ever see visible 'thermal damage' in a 6mm² bonding conductor? Bonding conductors very rarely carry any significant current for appreciable periods of time, and I would think that it would be incredibly rare for enough current to flow to thermally damage a 6mm² one, wouldn't it?
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Are these C2s or C3s
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I didn’t write out contribute to the BPG, I was just quoting what it says
But one member on here did contribute
Fair enough - but it seemed that you were making a statement of alleged 'fact', rather than quoting someone else's opinion.
Whatever, it would seem that whoever wrote what you quoted was rather daft (so maybe everything they wrote needs to be taken with a pinch of salt?). As EFLI and myself have said or implied, there must be very few bonding conductors around that have ever been subjected to a current high enough to result in thermal damage - so the absence of visible 'thermal damage' means absolutely nothing!
Indeed I do - and it is that very common sense which tells me that the fact that a bonding conductor shows no signs of thermal damage means absolutely nothing in terms of the adequacy of the conductor (hence whether it should be a C2 or C3), since it's very probable that it's never been subjected to a current anywhere near high enough to cause thermal damage. However, whoever wrote what you quoted presumably did not have the understanding or common sense to realise that.
I have, and the bit we're talking about is but one of many things it says which I personally regard as questionable.
So as a DIYer does it even matter to you.
If a home has existing 6mm then it’s ok. Of it has no bonding then 10mm needs to be installed
At the end of the day a considerable number of people came together to agree the codes.
That’s good enough for me AND the NICEIC direct their sparks to use the guide. AND it’s the only document in the public domain that customers have access to and can download for free
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@plugwash has said what I also consider the problem with an EICR, each edition of BS7671 has two things, one is new rules, and two is clarification of old rules. New rules can state if this then that, like 2008 with bathrooms, so if you fit an RCD you don't need to bond, or they can take account of other new practices, like using the car as a battery for the house, and redress a new problem like lack of bidirectional devices, which means in real terms.
If all is as it was when designed, it still complies with the regulations, but this it's never going to be the case, from the 1966 change in earth to light fittings to more modern changes, we look at statements like
So the PIR (periodic inspection report) when it changed to an EICR dropped Code 4 (does not comply with current edition) and it is left to the inspector to decide what is a "prospective danger" and one has to face it, 230 volts AC is always a prospective danger, so no one can say it is not a C2.
The phrase is, let the courts decide, but who wants to take it to court? As to the "best practice guide", they showed an overloaded socket with items hanging from the socket in a dangerous way as a fail. (code C2) But the plugs and cables are not part of the installation, so how can anything which is not part of the installation be taken into consideration with an installation report. The same applies when a builder comes in and runs dehumidifiers etc. Even if it's not safe, it is not part of the remit, same applies to lack of smoke alarms. It may be dangerous not having them, but having them fitted or not, is not part of the remit.
If all is as it was when designed, it still complies with the regulations, but this it's never going to be the case, from the 1966 change in earth to light fittings to more modern changes, we look at statements like
running without an earth to lights was not allowed even before 1966 for modern LED bulbs.13th edition said:
So the PIR (periodic inspection report) when it changed to an EICR dropped Code 4 (does not comply with current edition) and it is left to the inspector to decide what is a "prospective danger" and one has to face it, 230 volts AC is always a prospective danger, so no one can say it is not a C2.
The phrase is, let the courts decide, but who wants to take it to court? As to the "best practice guide", they showed an overloaded socket with items hanging from the socket in a dangerous way as a fail. (code C2) But the plugs and cables are not part of the installation, so how can anything which is not part of the installation be taken into consideration with an installation report. The same applies when a builder comes in and runs dehumidifiers etc. Even if it's not safe, it is not part of the remit, same applies to lack of smoke alarms. It may be dangerous not having them, but having them fitted or not, is not part of the remit.
As a "DIYer", it does not matter to me. However, as a person, I worry when I see so-called professionals (in any discipline) making or supporting statements which appear illogical and/or which cast doubts on their understanding of the profession they practice.
Anyone who can write (and I now accept that you were quoting others, not expressing your own opinion) ....
... either does not understand the electrical principles and/or does not have enough common sense to be practising as an electrician, let alone 'advising' electricians.
Well, for what it's worth, I would then say that that "considerable number of people", yourself and NICIEC all 'ought to know better' than to subscribe to that daft statement I quote above.
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Bottom line is if a landlord engages an electrician to do a safety check then he has to pay him whether he likes the report or not, unless it is so obviously flawed that he would win a court case over not paying. And even then he'd need to fork out for an expert witness and deal with the fact that he'd still be liable to fix problems within a certain time.
Is it really beyond the wit of man to come up with unambiguous pass/fail criteria for things?
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An oft-discussion question. Given the present situation, it would clearly be desirable for 'rules' regarding EICRs to be much more prescriptive, hence considerably reducing the amount of allowable 'judgement'/'discretion'/interpretation/opinion, on the part of both individuals producing EICRs and those (generally 'self-appointed') organisations who make attempts to 'advise' them.
MOTs have managed to go a long way down that road, but there always will be a need (with both MOs and EICRs) to allow inspectors to exercise some 'judgement' (of things which are not easily quantified).
However, as I always say, and particularly unless/until things do get a lot more prescriptive (and more particularly since legislation has given some 'teeth' to EICRs), I personally strongly feel that there should be much more (well-policed) regulation of who is allowed to conduct EICRs - requiring them to be registered/licenced, and subjected to enough policing/oversight to enable those whose EICRs are 'not acceptable' to be banned from undertaken them.
Bonding conductors can carry two types of current.
The first is "fault currents", a fault happens somewhere and some proportion of the fault current flows through the bonding system. IIRC in a domestic/light commercial setting, a 6mm² bonding conductor will almost-certainly be enough to handle these.
The second is "circulating network currents". On a TN-C-S system bonding conductors are essentially in parallel with neutral conductors and may carry part of the neutral current. Even if your property isn't TN-C-S, such current flows could happen via other properties. As a result of this there is a table of minimum sizes for TN-C-S bonding conductors based on the size of the supply neutral conductor. In a domestic situation this nearly always works out to 10mm²
Is being "one-size down" of a figure that will always be somewhat of a "guestimate" really bad enough to fail an installation.
Yes, I understand all that.
Indeed so.
I certainly wouldn't think so - as you say, it's only a guesstimate that has not quite been 'satisfied'.
However, that's not what I've been talking about. We seem to be agreed that a 6mm² main bonding conductor in a TN-C-S installation does not deserve a C2. My problem was with the statement (apparently originating from 'people who should know better') that 6mm² is 'OK' (just C3) "IF there are no signs of thermal damage". As I've said, it's so rare for a bonding conductor to be exposed to a current remotely high enough to cause thermal damage that it's surely inappropriate (aka 'ridiculous')) to draw any 'reassurance' from the fact that signs of thermal damage are absent, isn't it?
Conversely, the presence of thermal damage to bonding conductors would be a massive alarm bell.
Of course it would be - but, as you presumably understand, that is not the point.
Virtually all main bonding conductors 'show no signs of thermal damage', and that would undoubtedly still be essentially true if they were all 1mm² or smaller - NOT because the absence of thermal damage indicated that they had an adequate CSA for their intended purpose but, rather, because they had never been subjected to a sustained ("circulating network") current high enough to do thermal damage to anything!
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