That scenario is not one of the reasons for doing supplementary bonding.
Earth bonding regulations
- Thread starter davebullocklive
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It is, indeed, not one of the reasons for supplementary bonding being required.
However, if, having weighed up the pros and cons, someone really wanted to take some measures to reduce the danger to which eric refers (which, in practice, would only arise if the CH plumbing were somehow electrically floating), one would really need to see into the mind of the designer to know whether those measures were 'earthing'or 'bonding'. If the designer's intent was that the measures (s)he took would result in an OPD or RCD operating in the (very improbable) scenario eric mentioned, then I think we would agree that this was 'earthing'. However, if the intent of the designer's measures was to minimise the pd between the (usually floating) CH metalwork and (earthed) exposed-c-ps in that scenario, then, at least in terms of the way I was brought up, that would constitute 'bonding' - even though it is not a type of bonding ('supplementary' or otherwise) required by the regs.
Of course, the confusion arises since, although we can debate the use of these two words, the bit(s) of G/Y cable don't know whether they are'earthing' or 'bonding' conductors - so will, in the sort of situation we are discussing, unavoidably serve both purposes, whether the designer 'intended' that or not.
Kind Regards, John
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What every the reason or what ever the name given to a green and yellow wire it is not important.
What is important is to know what is the current installation.
1) Is it TT or TN?
2) Is there RCD protection on all circuits?
3) If answer to 2 is yes what is the current rating of the RCD?
4) Is the water pipe metal or plastic.
5) Is the gas pipe metal or plastic.
The last statement is important as that "insulating section or insert" stops your earth from being connected to next doors earth or causing the erosion of the pipe work.
I do worry where we just jump in with both feet and say earth it. Maybe because years ago I did just that and the result was all the earth leakage circuit breakers were rendered useless. I had not entered the caravans and did not realise they had the old voltage operated ELCB's fitted.
If the EICR says fit an earth wire fit it. If you have not had an EICR then get one done. With a house where you don't know the history there can be many faults where the DIY'er has made errors. So best option is to have the house tested.
I remember looking at my mothers house and finding some one (likely my dad) had connected the Telephone party line earth electrode to the consumer unit as the main earth it was no where near good enough. It's just too easy to make errors advising on a forum.
What is important is to know what is the current installation.
1) Is it TT or TN?
2) Is there RCD protection on all circuits?
3) If answer to 2 is yes what is the current rating of the RCD?
4) Is the water pipe metal or plastic.
5) Is the gas pipe metal or plastic.
The last statement is important as that "insulating section or insert" stops your earth from being connected to next doors earth or causing the erosion of the pipe work.
I do worry where we just jump in with both feet and say earth it. Maybe because years ago I did just that and the result was all the earth leakage circuit breakers were rendered useless. I had not entered the caravans and did not realise they had the old voltage operated ELCB's fitted.
If the EICR says fit an earth wire fit it. If you have not had an EICR then get one done. With a house where you don't know the history there can be many faults where the DIY'er has made errors. So best option is to have the house tested.
I remember looking at my mothers house and finding some one (likely my dad) had connected the Telephone party line earth electrode to the consumer unit as the main earth it was no where near good enough. It's just too easy to make errors advising on a forum.
Indeed so. I find it rather ironic that people are often very quick to stress (correctly) that a conductor with a certain function does not know what colour insulation it has yet, when we're talking G/Y, some people can get very excited about whether it is providing 'earthing' or 'bonding' - particular when the two functions are usually inseparable.
Maybe important in some senses, but (as we often discuss) also indicative of the fact that whoever wrote that regulation does not seem to have any understanding about the nature, or reason for, main equipotential bonding. If there is such an 'insulating section' (or insulating meter), then there is no point/need for "MEB" downstream of the insulating section/meter. Any connection one made to the pipework downstream of that electrical discontinuity would be 'earthing' (and certainly not 'main equipotential bonding') - and, as you have indicated, there are pros and cons of doing that to be considered, since, in some situations, it could increase risks.
Kind Regards, John
It may not be important in that whether you use the correct term or not does not alter the purpose and function.
However, if you use the incorrect term then other people do not know what you mean.
What is often ignored is extraneous-conductive-parts including the following:
(i) Water installation pipes
(ii) Gas installation pipes
(iii) Other installation pipework and ducting
(iv) Central heating and air conditioning systems
(v) Exposed metallic structural parts of the building.
It is not a list of parts that must be bonded.
It is not we who are jumping in nor is that said by people who understand earthing and bonding.
Only if the inspector is correct.
If the inspector says fit an earth wire when referring to bonding I would suspect his ability and, therefore, other recommendations.
Have you got that right?
I fail to see the irony; it is the colour that is irrelevant, not the function.
If you are referring to the pointing-out to DIYers that a blue or black switched-live wire is not a neutral - then entirely correct.
They are not inseparable.
There is no reason to purposely earth a pipe but they may require bonding because they are earthed.
Indeed so. As you imply, it is a (non-exhaustive) list of things which may be extraneous-c-ps and which, IF they are, must have main bonding.
Kind Regards, John
That certainly was the first bit of what I was talking about, but maybe what I wrote was a bit confused. I suppose the point I was trying to make is the one (in the rest of my sentence) with which you go on to disagree, about the fact that the two functions may be 'inseparable' ....
Hmmm. As I thought I illustrated, I'm not sure that's true in relation to hypothetical scenarios such as eric presented (much akin to the metal bath one). IF, as eric was doing, a designer wishes to contemplate (and attempt to minimise the danger of) the remote possibility of a piece of floating (i.e. not earthed) metal coming in contact with the live filament of a broken lamp/bulb in a toppled over standard lamp, creating a high pd between that floating metalwork and any (earthed) exposed-c-ps, then the only way in which (s)he can take steps to reduce the danger of that (very improbable) scenario is to connect the (floating, not earthed) metalwork in question through a bit of G/Y cable to some part of the installation's earthing system.
The designer may think of that bit of G/Y as minimising the pd which can exist between the (not earthed) pipes/radiators and (earthed) exposed-c-ps - in which case I would call that 'bonding', wouldn't you? (if not, what is your definition of 'bonding'?). On the other hand, the designer may think of that bit of G/Y as creating a situation in which eric's theoretical event would result in a protective device (OPD or RCD) operating, thereby removing the potential danger - and I think we would all agree that is 'earthing'. However, there is no way to 'tell' the G/Y to achieve one of those things but not the other - which is why I think that what one calls the function of the conductor is pretty moot, and that, in that situation, the 'two functions' of that the G/Y are pretty 'inseparable'.
I don't expect you to agree
Kind Regards, John
Suffice to say that I think Eric's hypothetical scenario is fatuous.
Should his lamp fall regularly then he may consider earthing the pipe desirable to disconnect the supply. He may then consider bonding other pipes to the first to reduce pd between them.
However, securing or disposal of the lamp would be a much more satisfactory procedure.
There would be no pd therefore the first connection would be earthing.
If the pipes are not earthed they cannot be bonded to a exposed-c-p.
A protective conductor providing equipotential bonding - where have I seen that before?
Yes, the first connection to an otherwise isolated part.
That, obviously, is the result but it does not detract form the original reason for its implementation.
If, as in my description above, the first earthing conductor were removed the remaining bonding conductors would not provide an earthing function.
Take an example of a worrier deciding to isolate all the copper pipe in his home by inserting plastic sections at all the relevant positions (entry, boiler, immersion etc.).
Eric buys the property.
Would it be wise for him to earth his isolated visible central heating pipes because of his wobbly lamp?
I don't expect you to agree
If a metal object is not part of the electrical installation, or an electrical appliance, it cannot be earthed.
Indeed, that's the second "designer's thought process" I discussed. However, as I said, eric (or some other designer) might think differently ...
There would be no pd (between the floating pipework/radiators and any earthed exposed-c-ps in the vicinity at the time one installed one's G/Y, but in the absence of any G/Y, there obviously would be a (large) pd between those two things should the live filament of eric's broken lamp come in contact with the floating pipework/radiators. Adding the G/Y would (largely) prevent such a pd ever arising under fault conditions. It's really no different from installing Main Bonding- it's very probably that there would be little or no pd between the MET and extraneous-c-ps just before one installed the main bonding conductor - the reason one applies the MPB is to prevent any significant pd arising between extraneous-c-p and MET under fault conditions in the future.
Why not? All a bonding conductor does is to ensure that the two things joined remain essentially equipotential under all (including fault) circumstances - that, per my upbringing, is what 'bonding' means - and one can 'bond together' any two things that one wants. Of course, the 'confusion' again arises, since by installing such a bonding conductor, one would also have 'earthed' the previously non-earthed metalwork! I think the problem here is probably that you have the fixed idea that (and per the common/usual situation) one bonds in order to prevent the introduction of earth potential producing pds and problems, in which case one would clearly not bond something that was not already earthed (or likely to become earthed). However, one (eric?) may also want to bond if there is a perceived risk that a conductor might at some point in the future introduce a 230V potential - in which casethe adage that "one only bonds something which is already earthed" clearly becomes a nonsense.
You seem to be playing 'mind reader'. As I've said, in the minds of some designers, "the original reason for the implementation" may have been to ensure that the CH metalwork and exposed-c-ps remained essentially equipotential, even in the very improbably occurrence of an 'eric event'.
"Wise", or "what I would do" are not what we're talking about - but I can see that some designers might take that view.
Kind Regards, John
The concept of earthing cannot apply to something which is not an exposed-conductive-part.
If you create a connection between such an object and the installation earth you have bonded it, not earthed it.
If you create a connection between such an object and the installation earth you have bonded it, not earthed it.
But the pipes in question are being considered exposed-c-ps.
They could be considered as erotica, but it wouldn't make them so.
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