More on meters and 544.1.2

[JohnW2]

Good thread John. For all but new builds, then the liklihood is, that either/and/or the metal services (if these exist) are connected by supplementary bonding elsewhere in the house or have situations where metal pipes feed metal pipes connected to metal drain pipes or has a metal pipe running to an outbuilding etc. Any condideration of where/how to bond on customers side of the meter should take those possibilities into account (which is what I think you have done? ) and was the point of my earlier post EFLI.

Thanks. However, having recently given my take on what I feel the regs should say (on the basis of electrical considerations), we get back to the whole point of the thread, which is to try to decide whether the regs would actually be satisfied by working to the 'John regs' - and, because of the way the regs are written, I still don't really know the answer to that!

In situations in which the regs, righly or wrongly, call for MPB, 'incidental' connections between pipework and MET via supplementary bonding and/or CPCs would obviously not satisfy the regs, either in terms of location of the bonding or conductor CSA.

Kind Regards, John

 

[EFLImpudence]

1...If a service enters the premises in plastic, there is no extraneous-c-p. No need for any MPB.

Agreed.

2...If a service enters the premises in metal, and it is practicable, bond as close as possible to the point of entry.

Agreed.

3...If a service enters the premises in metal but then fairly quickly changes to plastic then, if it is practicable, bond the metal pipe as close as possibly to entry, per (2). If that is not practicable, then one simply can't. There is nothing else to bond.

Agreed.

4...The issue of a service which enters the premises in metal but soon encounters a short "insulation section or insert" (before turning back to metal) is really irrelevant. Once pipe has turned to plastic, there is no electrical need for MPB for any downstream pipework, even if it reverts to being metal. Therefore treat as (3) above.

Agreed.

4a...As discussed, I don't know if (some or all) meters represent 'insulating sections' or not. If there is no electrical continuity across a meter, one could proceed as per (4).

Agreed.

However, if there is,or may be, electrical continuity and it is not practicable to bond prior to the meter (as close as possible to entry), then bond as close as practicable after the meter (and before any stopcocks or branches etc.).

Agreed but assumes the meter is close to the point of entry.

Given that meters get changed, the 'safe aproach' may be to assume that, even if at present 'insulating', a meter might get changed to one with electrical continuity (or the water supplier might install a 'strap') - so (when pre-meter bonding is not practicable) always bonding as close as practicable after the meter (in addition to bonding prior to the meter, if practicable - for times when the meter is insulating!) might be sensible.

Agreed.
However, if the meter presented a resistance (not sure how but just for example), would you consider bonding prior or after the meter would be safer or would you bridge the meter?

In other words, does a resistance on the consumer's side of any main bonding (so not quite at true earth) increase or decrease the hazard in the event of a fault?

Therefore, does bonding at the point of entry or after the meter cover all eventualities better assuming pipes are not isolated?

That's about it. I think that, in terms of the electrical need for MBP, it is (or should be!) as simple and clear as that. The nearest to a 'messy' bit is that about the meter - but that's because of uncertainties (at least, in my mind) as to whether it is (or always will be) 'insulating' or not.

Agreed but with the above proviso.

However, having said all that, there is a practical consideration which may change all that, and make things considerably simpler. As I recently observed, although there are situations (3 & 4 above) in which there is no electrical requirement for MPB of the house's metal pipework, one may, in practice, want to install such bonding in order to ensure that the requirements for omitting supplementary bonding in bathrooms are always satisfied.

That is not really necessary is it?
Non-extraneous-parts do not require bonding to satisfy 701.415.2

As we've also discussed, although there is a theoretical argument that such 'unnecessary bonding' could (in certain circumstances) create a hazard, this is really moot because of the other incidental paths from pipework to MET which will almost certainly exist. If one wishes to take this approach, then the main bonding practice (which goes beyond the electrical MPB requirement) would simplify to just:

Agreed. Main bonding non-extraneous water pipes which are connected to extraneous-parts and cpcs is not detrimental - in effect supplementary bonding.
However, this should not be done to totally isolated pipes so doing it 'willy-nilly' without testing/measuring could create a hazard.

1...If a service enters the premises in metal, bond as close as practicable to the point of entry (if the metal pipe is too short/inaccessible to bond, then it simply can't be done). In addition bond the house's metal pipework after any 'insulating interruption'.

I'm not sure why you have added this bit.
Is it not the same as '4' ?

 

[JohnW2]

Agreed. ... Agreed. ... Agreed. ... Agreed. ... Agreed.

My goodness

However, if there is,or may be, electrical continuity and it is not practicable to bond prior to the meter (as close as possible to entry), then bond as close as practicable after the meter (and before any stopcocks or branches etc.).

Agreed but assumes the meter is close to the point of entry.

Not really. As you quote, I did say "... and if it is not practicable to bond prior to the meter ...". One would assume that, with very rare exceptions, if the meter were not close to the point of entry then it would be possible to bond prior to the meter, wouldn't one?

Agreed. However, if the meter presented a resistance (not sure how but just for example), would you consider bonding prior or after the meter would be safer or would you bridge the meter?...

As I've said, whenever it is practicable, one should bond before the meter - in which case that's all that's required. If that is not possible, and if there is any suggestion that the meter might be (or become) 'conductive' (i.e. doesn't electrically isolate the house's pipework from the extraneous-c-p), then one should bond (as close as possible) on the consumer's side of the meter.

...In other words, does a resistance on the consumer's side of any main bonding (so not quite at true earth) increase or decrease the hazard in the event of a fault?

I'm not sure whether my answer above answers this. If it doesn't could you perhaps rephrase your question a bit?

Therefore, does bonding at the point of entry or after the meter cover all eventualities better assuming pipes are not isolated?

Ah, perhaps I'm starting to understand your point/question. From the POV of the need for main bonding, if one can bond at the point of entry, then that surely 'covers all eventualities', doesn't it? From the MPB point-of-view, one surely has to think about whether post-meter bonding might be required (or desirable, for 'safety') only if it has not been possible to bond pre-meter?

However, having said all that, there is a practical consideration which may change all that, and make things considerably simpler. As I recently observed, although there are situations (3 & 4 above) in which there is no electrical requirement for MPB of the house's metal pipework, one may, in practice, want to install such bonding in order to ensure that the requirements for omitting supplementary bonding in bathrooms are always satisfied.

That is not really necessary is it? Non-extraneous-parts do not require bonding to satisfy 701.415.2

Yuk - another matter of interpretation of the regs ... As you know, 701.415.2(vi) gives one of the conditions for omission of supplementary bonding as:

"All extraneous-conductive-parts of the location are effectively connected to the protective equipotential bonding ..."

I have always taken 'at the location' as referring to the bathroom, so that any pipe entering the bathroom 'which is liable to introduce a potential, usually earth potential' (which will be true of virtually any metal pipe in virtually any house) constitutes an "extraneous-conductive-part of the location". Do you disagree? If one adopts that interpretation, then there appears to be a requirement (if one wishes to avoid supplementary bonding) to ensure that the pipe is 'effectively connected' to the the MEB - which to my mind requires that pipework to be formally main bonded (somewhere), rather than relying on 'incidental' paths from pipework to MET. Again, do you disagree?

Agreed. Main bonding non-extraneous water pipes which are connected to extraneous-parts and cpcs is not detrimental - in effect supplementary bonding.

Glad you agree.

However, this should not be done to totally isolated pipes so doing it 'willy-nilly' without testing/measuring could create a hazard.

No argument there - but, as I'm always saying, I really don't think you are likely to find any "totally isolated" metal pipes in a house with (totally or mainly) metal pipework. It obviously could happen if someone used one or two bits of copper pipe in what was otherwise a plastic-plumbed premises - and, no, I obviously would not bond those bits of isolated copper.

1...If a service enters the premises in metal, bond as close as practicable to the point of entry (if the metal pipe is too short/inaccessible to bond, then it simply can't be done). In addition bond the house's metal pipework after any 'insulating interruption'.

I'm not sure why you have added this bit. Is it not the same as '4' ?

No, it's fundamentally different from (4). My (4) says that one does not bond after an insulating interruption (which satisfies electrical MPB considerations). This alternative says that one does bond after the insulating operation (as well as before, if that is practicable) [if one wishes, and feels this is necessary to satisfy 701.415.2(vi)]

Kind Regards, John

 

[EFLImpudence]

Therefore, does bonding at the point of entry or after the meter cover all eventualities better assuming pipes are not isolated?

Ah, perhaps I'm starting to understand your point/question. From the POV of the need for main bonding, if one can bond at the point of entry, then that surely 'covers all eventualities', doesn't it? From the MPB point-of-view, one surely has to think about whether post-meter bonding might be required (or desirable, for 'safety') only if it has not been possible to bond pre-meter?

Say, there were a resistance between the main bond correctly installed at the point of entry and somewhere else in the house then surely the pipes on the consumer side of this resistance will not be sufficiently bonded.
That is they may, if long enough, still have an impedance between a fault and the bond and hence the MET. Is this not the same as not being at the same potential?
Or is that too much to have to prevent?
Is that why bonding on the consumer's side of meters is 'recommended'?

That is not really necessary is it? Non-extraneous-parts do not require bonding to satisfy 701.415.2

Yuk - another matter of interpretation of the regs ... As you know, 701.415.2(vi) gives one of the conditions for omission of supplementary bonding as:

"All extraneous-conductive-parts of the location are effectively connected to the protective equipotential bonding ..."

I have always taken 'at the location' as referring to the bathroom, so that any pipe entering the bathroom 'which is liable to introduce a potential, usually earth potential' (which will be true of virtually any metal pipe in virtually any house) constitutes an "extraneous-conductive-part of the location". Do you disagree?

Surely if it is not extraneous at the entry to the property and so does not require bonding then it will not require bonding for the purposes of 701.415.2(v).
If over 23kΩ between point of entry and MET won't it be >23kΩ between this pipe and other things in the bathroom?

If one adopts that interpretation, then there appears to be a requirement (if one wishes to avoid supplementary bonding) to ensure that the pipe is 'effectively connected' to the the MEB - which to my mind requires that pipework to be formally main bonded (somewhere), rather than relying on 'incidental' paths from pipework to MET. Again, do you disagree?

Only if it is extraneous and/or would actually require supplementary bonding.

However, this should not be done to totally isolated pipes so doing it 'willy-nilly' without testing/measuring could create a hazard.

No argument there - but, as I'm always saying, I really don't think you are likely to find any "totally isolated" metal pipes in a house with (totally or mainly) metal pipework. It obviously could happen if someone used one or two bits of copper pipe in what was otherwise a plastic-plumbed premises - and, no, I obviously would not bond those bits of isolated copper.

Quite.
I know isolated pipes are likely in a 'normal' house but have to make the point because someone else may read this.
Plus if the pipes are not isolated then they will/should be main bonded.

1...If a service enters the premises in metal, bond as close as practicable to the point of entry (if the metal pipe is too short/inaccessible to bond, then it simply can't be done). In addition bond the house's metal pipework after any 'insulating interruption'.

I'm not sure why you have added this bit. Is it not the same as '4' ?

No, it's fundamentally different from (4). My (4) says that one does not bond after an insulating interruption (which satisfies electrical MPB considerations). This alternative says that one does bond after the insulating operation (as well as before, if that is practicable) [if one wishes, and feels this is necessary to satisfy 701.415.2(vi)]

But I don't think it is.

If it did not require main bonding then it won't require supplementary bonding so you would be introducing hazards by so doing.

 

[JohnW2]

Say, there were a resistance between the main bond correctly installed at the point of entry and somewhere else in the house then surely the pipes on the consumer side of this resistance will not be sufficiently bonded.

Are you not overlooking the (one and only) reason for main bonding - namely to prevent a PD arising within the house by virtue of a difference in potential between the house's MET and the potential introduced (from outside the premises) by an incoming service pipe?

That is they may, if long enough, still have an impedance between a fault and the bond and hence the MET. Is this not the same as not being at the same potential?

As above, although what you say is true, it is not something which MPB is designed to address. MPB seeks only to prevent PDs arising because of potentials introduced from outside the property. Ironically, the hazard you are now describing may result from not directly bonding the house's pipework to the MET (when the service has been bonded prior to an 'insulating section') - something which many people (I think including yourself) have been known to argue is unnecessary, if not 'dangerous'.

Let's face it, the hypothetical situation I think you are postulating (of a meter which represents a finite. but neither very low nor very high, resistance) is merely a lesser example of the more extreme case of household pipework which is totally insulated/isolated from a bonded extraneous-c-p (e.g. by an 'insulating section'). I though we had agreed that, in such a situation, MPB considerations do not require that pipework to be bonded

Is that why bonding on the consumer's side of meters is 'recommended'?

As I've said, if such bonding were required (by regs), which I don't think it is, it would be supplementary, rather than main, bonding.

[Surely if it is not extraneous at the entry to the property and so does not require bonding then it will not require bonding for the purposes of 701.415.2(v).

As I said, 701.415.2(vi) refers to "extraneous to the location" and, as I also said, I have always taken that 'location' to mean the bathroom, not the property. That view is perhaps re-inforced by the fact that the title of Chapter 701 is "Locations containing a bath or shower" - and you surely don't believe that 'location' there refers to the whole property, rather than just the bathroom?! I take it that you disagree with this interpretation?

If over 23kΩ between point of entry and MET won't it be >23kΩ between this pipe and other things in the bathroom?

That's surely the whole point. As I said, thanks to CPCs and exposed-conductive parts, one would expect metal pipework entering a bathroom to have probably <1&#937; to the MET, not >23k&#937;, wouldn't one?

Plus if the pipes are not isolated then they will/should be main bonded.

Will/should they? I thought that was what we were discussing. I thought we had agreed that if the service was main bonded at or near the point of entry, there was no need to main bond house pipework beyond a subsequent 'insulatting section' or whatever.

If it did not require main bonding then it won't require supplementary bonding so you would be introducing hazards by so doing.

This all depends on the interpretation of "extraneous to the location" in 701.415.2(vi), about which our views appear to differ!

Kind Regards, John

 

[EFLImpudence]

Ironically, the hazard you are now describing may result from not directly bonding the house's pipework to the MET (when the service has been bonded prior to an 'insulating section') - something which many people (I think including yourself) have been known to argue is unnecessary, if not 'dangerous'.

That would only be when totally isolated parts are 'bonded incorrectly' (earthed).
I have said above this would not be detrimental if already connected to other parts.

[Surely if it is not extraneous at the entry to the property and so does not require bonding then it will not require bonding for the purposes of 701.415.2(v).

As I said, 701.415.2(vi) refers to "extraneous to the location" and, as I also said, I have always taken that 'location' to mean the bathroom, not the property. That view is perhaps re-inforced by the fact that the title of Chapter 701 is "Locations containing a bath or shower" - and you surely don't believe that 'location' there refers to the whole property, rather than just the bathroom?! I take it that you disagree with this interpretation?

If pipes cannot introduce earth potential into the property as a whole, how can they introduce it into the bathroom?
If the water pipes can only introduce earth potential because of their connection to the gas pipes then the gas pipe main bonding will be sufficient and negate this.

If over 23k&#937; between point of entry and MET won't it be >23k&#937; between this pipe and other things in the bathroom?

That's surely the whole point. As I said, thanks to CPCs and exposed-conductive parts, one would expect metal pipework entering a bathroom to have probably <1&#937; to the MET, not >23k&#937;, wouldn't one?

Yes, but that is just the cut-off point to determine whether extraneous.

I did only realise what you had in mind just after I posted my previous reply.
However, the pipes cannot, surely, be extraneous in the bathroom if not in the whole installation.
Taking the whole installation, if connecting non-extraneous water pipes to the extraneous gas pipes does not make them require main bonding then why are they any different in the bathroom?
If the water pipes can only introduce earth potential because of their connection to the gas pipes then the gas pipe main bonding will be sufficient and negate this.

Plus if the pipes are not isolated then they will/should be main bonded.

Will/should they?

Yes.

I thought that was what we were discussing. I thought we had agreed that if the service was main bonded at or near the point of entry, there was no need to main bond house pipework beyond a subsequent 'insulatting section' or whatever.

Yes but in your bathroom scenario we are talking about pipes which are NOT main bonded.
If they were then you can omit your supplementary anyway.

If it did not require main bonding then it won't require supplementary bonding so you would be introducing hazards by so doing.

This all depends on the interpretation of "extraneous to the location" in 701.415.2(vi), about which our views appear to differ!

I was thinking about isolated pipes so this was incorrect.

 

[JohnW2]

Ironically, the hazard you are now describing may result from not directly bonding the house's pipework to the MET (when the service has been bonded prior to an 'insulating section') - something which many people (I think including yourself) have been known to argue is unnecessary, if not 'dangerous'.

That would only be when totally isolated parts are 'bonded incorrectly' (earthed). I have said above this would not be detrimental if already connected to other parts.

Yes, we've agreed that it would not be detrimental, except (just about) in the pretty rare event of a truly 'totally isolated' bit of metal pipework. However, I thought that in the context of this discussion (and previous discussions), we had agreed that pipework after an 'insulating section' (i.e. not in continuity with any extraneous-c-p) did not need any main bonding?

If pipes cannot introduce earth potential into the property as a whole, how can they introduce it into the bathroom?

Again, it totally depends upon how one interprets "extraneous to the location" in 701.415.2(vi), and we seem to disagree about that. We are both saying things which are consistent with our personal interpretations of the meaning of that phrase but, because our interpretations differ, so do our conclusions! I don't know how we resolve this one. I suppose that some additional opinions would help.

If the water pipes can only introduce earth potential because of their connection to the gas pipes then the gas pipe main bonding will be sufficient and negate this.

Don't forget that an extraneous-c-p is defined as a conductor which is "liable to to introduce a potentially, generally [but not necessarily] Earth potential". If one takes my view that, in 701.415.2(vi), 'location' means bathroom, then there is no doubt in my mind that a metal water pipe will usually "be liable to introduce a potential into that location" - and the rest of my argument follows from that. However, if you are working with a different definition of 'location', you will not agree with me.

However, the pipes cannot, surely, be extraneous in the bathroom if not in the whole installation.

See above. The pipes certainly can be extraneous to the bathroom, if one accepts the BS7671 definition which only requires them to introduce a potential (not necessarily Earth potential) into the location (which I consider to be the bathroom).

I won't comment specifically on the rest of what you wrote because again, what you say is all consistent with your interpretation of 701.415.2(vi), but equally not consistent with my interpretation!

Kind Regards, John

 

[JohnW2]

Surely if it is not extraneous at the entry to the property and so does not require bonding then it will not require bonding for the purposes of 701.415.2(v).

If pipes cannot introduce earth potential into the property as a whole, how can they introduce it into the bathroom?

I've just realised that there's a crucial point I haven't made (I fear because I thought it was 'obvious'!) in this part of the discussion...

...I agree entirely with you that it appears to be nonsense for 701.415.2(vi) to require that pipework which (from the point of view of the property as a whole) didn't require to be main bonded in the first place to be 'effectively connected' to the PEB if one wants to omit supplementary bonding. However, what I am saying is that I believe 701.415.2(vi), coupled with the BS7671 definition of 'extraneous-c-p', actually is introducing that (seemingly nonsensical) requirement. It would make more sense for there to be a requirement for the pipework to be 'effectively connected' to the MET - but that, of course, would still make sense even if there was nothing in the property which required any MPB.

Kind Regards, John

 

[EFLImpudence]

Ironically, the hazard you are now describing may result from not directly bonding the house's pipework to the MET (when the service has been bonded prior to an 'insulating section') - something which many people (I think including yourself) have been known to argue is unnecessary, if not 'dangerous'.

That would only be when totally isolated parts are 'bonded incorrectly' (earthed). I have said above this would not be detrimental if already connected to other parts.

Yes, we've agreed that it would not be detrimental, except (just about) in the pretty rare event of a truly 'totally isolated' bit of metal pipework. However, I thought that in the context of this discussion (and previous discussions), we had agreed that pipework after an 'insulating section' (i.e. not in continuity with any extraneous-c-p) did not need any main bonding?

In that case it is not one one which I have previously argued was dangerous.

If the water pipes can only introduce earth potential because of their connection to the gas pipes then the gas pipe main bonding will be sufficient and negate this.

Don't forget that an extraneous-c-p is defined as a conductor which is "liable to to introduce a potentially, generally [but not necessarily] Earth potential".

Fair enough but it still applies to the bathroom as it does to the whole installation.
If it definitely is extraneous in the bathroom then it is extraneous in the whole installation and should be main bonded.

If one takes my view that, in 701.415.2(vi), 'location' means bathroom, then there is no doubt in my mind that a metal water pipe will usually "be liable to introduce a potential into that location" - and the rest of my argument follows from that.

As above.

However, if you are working with a different definition of 'location', you will not agree with me.

I am not but is is only in the location of the bathroom that supplementary bonding is required.
I just do not see how parts become extraneous when they are in a 'location' when they were not the other side of the wall.

However, the pipes cannot, surely, be extraneous in the bathroom if not in the whole installation./quote]
See above. The pipes certainly can be extraneous to the bathroom, if one accepts the BS7671 definition which only requires them to introduce a potential (not necessarily Earth potential) into the location (which I consider to be the bathroom).

But then they must be extraneous outside of the location and should be main bonded at the point of entry to the premises.

701.415.2(vi) states(along with the other conditions that supplementary bonding may be omitted if) All extraneous parts OF the location are effectively connected to the protective equipotential bonding according to Regulation 411.3.1.2
411.3.1.2 relates to main bonding but it is the supplementary bonding and people being wet which are peculiar to this location, not the conditions of the installation, so if the parts in question ARE extraneous in this location then they will be extraneous in other locations which do not require supplementary bonding and so should have been main bonded at the point of entry to the premises already.

It seems, from what you are saying, that there are instances where it could be necessary just to apply main bonding from, or outside of, a bathroom to the MET.
This is never the case. Even supplementary bonding does not connect to the MET.
As this is never the case, presumably the cause of this is never the case either.

 

[JohnW2]

Yes, we've agreed that it would not be detrimental, except (just about) in the pretty rare event of a truly 'totally isolated' bit of metal pipework. However, I thought that in the context of this discussion (and previous discussions), we had agreed that pipework after an 'insulating section' (i.e. not in continuity with any extraneous-c-p) did not need any main bonding?

In that case it is not one one which I have previously argued was dangerous.

Fair enough, but others certainly have (argued that it was dangerous) - probably because they have overlooked the fact that the pipework would almost always already be earthed, via one route or another. It's earthing (rather than leaving floating) the pipe (which would happen if it were bonded) that has concerned them.

I just do not see how parts become extraneous when they are in a 'location' when they were not the other side of the wall.

They obviously can't 'become extraneous' in the sense of being liable to introduce a potential from outside of the building as a whole. However, what I've been saying is that they can (and do) introduce a potential from outside of the location (room). As above, maybe I'm misinterpreting the regs.

701.415.2(vi) states(along with the other conditions that supplementary bonding may be omitted if) All extraneous parts OF the location are effectively connected to the protective equipotential bonding according to Regulation 411.3.1.2
411.3.1.2 relates to main bonding .....

I can see where you're coming from, but I suppose I've always tried to read more into it than a mere 'statement of the obvious'. If one one takes just the 'statement of the obvious' interpretation, it almost seems to be acknowledging the possibility that the installation may be seriously non-BS7671-compliant - since 411.3.1.2 obviously already requires any services which are extraneous to the premises to be main bonded, regardless of any consdieration of bathrooms.

Are you therefore simply interpreting 701.415.2(vi) as saying that you can't omit supplementary bonding in the bathroom if the installation is already non-compliant by not having the required main bonding of extraneous-c-ps (which is clearly a major issue in it's own right)? In other words, are you effectively saying that 701.415.2(vi) is essentially a total irrelevance, since it will inevitably be satisfied in any compliant installation? Surely any electrician would rectify the absence of main bonding in an installation before event starting to think about whether supplementary bonding could be omited in a bathroom?

It seems, from what you are saying, that there are instances where it could be necessary just to apply main bonding from, or outside of, a bathroom to the MET. This is never the case.

What I was suggesting is that one could interpret the reg as requiring that (if one wanted to omit supplementary bonding) the pipework within the bathroom had to be 'effectively connected to' the equipotential zone' (by whatever means) - i.e. that if there was 'floating' metal pipework, one had to have supplementary bonding (which would render it no longer floating!). However, if one works with your 'mere statement of the obvious' interpretation of 701.415.2(vi), then I accept that such is not the case.

... but all this discussion about bathroom supplementary bonding is really a distraction. When can we get back to 544.1.2 and the question of whether the 'common sense' set of rules I proposed would actually be compliant or not?

Kind Regards, John

 

[EFLImpudence]

They obviously can't 'become extraneous' in the sense of being liable to introduce a potential from outside of the building as a whole. However, what I've been saying is that they can (and do) introduce a potential from outside of the location (room). As above, maybe I'm misinterpreting the regs.

I think so.
If they could do that in the location (bathroom) then they could do it elsewhere and so ARE extraneous and should be main bonded.

701.415.2(vi) states(along with the other conditions that supplementary bonding may be omitted if) All extraneous parts OF the location are effectively connected to the protective equipotential bonding according to Regulation 411.3.1.2
411.3.1.2 relates to main bonding .....

I can see where you're coming from, but I suppose I've always tried to read more into it than a mere 'statement of the obvious'. If one one takes just the 'statement of the obvious' interpretation, it almost seems to be acknowledging the possibility that the installation may be seriously non-BS7671-compliant - since 411.3.1.2 obviously already requires any services which are extraneous to the premises to be main bonded, regardless of any consideration of bathrooms.

Yes, of course.

Are you therefore simply interpreting 701.415.2(vi) as saying that you can't omit supplementary bonding in the bathroom if the installation is already non-compliant by not having the required main bonding of extraneous-c-ps (which is clearly a major issue in it's own right)?

Yes, main bonding should be checked and rectified if necessary before ANY work is done.

In other words, are you effectively saying that 701.415.2(vi) is essentially a total irrelevance, since it will inevitably be satisfied in any compliant installation?

Not an irrelevance. It ensures the safety measures are satisfactory.

Surely any electrician would rectify the absence of main bonding in an installation before event starting to think about whether supplementary bonding could be omited in a bathroom?

Yes, of course. As above.
The same as condition (iv) that all disconnection times be met and (v) that RCDs are in place.

It seems, from what you are saying, that there are instances where it could be necessary just to apply main bonding from, or outside of, a bathroom to the MET. This is never the case.

What I was suggesting is that one could interpret the reg as requiring that (if one wanted to omit supplementary bonding) the pipework within the bathroom had to be 'effectively connected to' the equipotential zone' (by whatever means) - i.e. that if there was 'floating' metal pipework, one had to have supplementary bonding (which would render it no longer floating!).

No, definitely not. Think door handles and spoons.

However, if one works with your 'mere statement of the obvious' interpretation of 701.415.2(vi), then I accept that such is not the case.

I'm surprised you thought that.
It never occurred to me that was what you were thinking.

but all this discussion about bathroom supplementary bonding is really a distraction. When can we get back to 544.1.2 and the question of whether the 'common sense' set of rules I proposed would actually be compliant or not?

I think they would.
However, I am puzzled by the recommendation for main bonding after the insulating section.
Is it to ensure the above is satisfied because it makes no difference to pipes that are connected to other pipes and cpcs in any case?

 

[JohnW2]

Are you therefore simply interpreting 701.415.2(vi) as saying that you can't omit supplementary bonding in the bathroom if the installation is already non-compliant by not having the required main bonding of extraneous-c-ps (which is clearly a major issue in it's own right)?

Yes, main bonding should be checked and rectified if necessary before ANY work is done.

In other words, are you effectively saying that 701.415.2(vi) is essentially a total irrelevance, since it will inevitably be satisfied in any compliant installation?

Not an irrelevance. It ensures the safety measures are satisfactory.

I didn't mean irrelevance in the sense of 'unimportant'. I meant that the had no 'specific relevance' (to bathrooms). As I think you go on to agree, such 'conditions' regarding what should always be done to ensure that safety measures are satisfactory could be slipped into thousands of places in the regs (e.g. "You can have a ring final circuit, provided that ....." etc. etc. etc.), but they seem to have singled out supplementary bonding in bathrooms - which is why I thought it had to mean something specific, rather than just being a statement of generic safety checks/measures.

What I was suggesting is that one could interpret the reg as requiring that (if one wanted to omit supplementary bonding) the pipework within the bathroom had to be 'effectively connected to' the equipotential zone' (by whatever means) - i.e. that if there was 'floating' metal pipework, one had to have supplementary bonding (which would render it no longer floating!).

No, definitely not. Think door handles and spoons.

I've already said that, if that's what it meant, I would regard it as nonsensical - it's just that I thought that it was perhaps saying that (after all, it wouldn't be the first time we had an issue with the regs!)

but all this discussion about bathroom supplementary bonding is really a distraction. When can we get back to 544.1.2 and the question of whether the 'common sense' set of rules I proposed would actually be compliant or not?

I think they would. However, I am puzzled by the recommendation for main bonding after the insulating section. ... Is it to ensure the above is satisfied because it makes no difference to pipes that are connected to other pipes and cpcs in any case?

Well, having hopefully got the bathroom issue out of the way, 'my rules' would not have any main bonding after insulating sections - which is why I fear that 'my rules' may not actually be compliant! If it were impossible/'not practicable' to bond before the insulating section, my rules would not bond at all.

Kind Regards, John

 

[EFLImpudence]

What I was suggesting is that one could interpret the reg as requiring that (if one wanted to omit supplementary bonding) the pipework within the bathroom had to be 'effectively connected to' the equipotential zone' (by whatever means) - i.e. that if there was 'floating' metal pipework, one had to have supplementary bonding (which would render it no longer floating!).

No, definitely not. Think door handles and spoons.

I've already said that, if that's what it meant, I would regard it as nonsensical - it's just that I thought that it was perhaps saying that (after all, it wouldn't be the first time we had an issue with the regs!)

Just to say that I would have in the past said that was dangerous.
It's just I didn't realise that's what was meant.

However, I am puzzled by the recommendation for main bonding after the insulating section. ... Is it to ensure the above is satisfied because it makes no difference to pipes that are connected to other pipes and cpcs in any case?

Well, having hopefully got the bathroom issue out of the way, 'my rules' would not have any main bonding after insulating sections - which is why I fear that 'my rules' may not actually be compliant! If it were impossible/'not practicable' to bond before the insulating section, my rules would not bond at all.

It depends.
Can you argue that, as I have reported, if something IS not extraneous then 544.1.2 does not apply.

 

[JohnW2]

Just to say that I would have in the past said that was dangerous. It's just I didn't realise that's what was meant.

Fair enough. Anyway, I think we're agreed about this one now. Arguments about it being dangerous could only be entertained if the pipework in question really were totally floating, which is rarely going to arise (apart from little bits of copper pipe in otherwise plastic-plumbed installations, which neither of us would bond).

Well, having hopefully got the bathroom issue out of the way, 'my rules' would not have any main bonding after insulating sections - which is why I fear that 'my rules' may not actually be compliant! If it were impossible/'not practicable' to bond before the insulating section, my rules would not bond at all.

It depends. Can you argue that, as I have reported, if something IS not extraneous then 544.1.2 does not apply.

As I said before, I rather like that argument and, as I wrote to someone yesterday, I'm becoming increasingly inclined to adopt that view/ approach. I fear, however, that Mr Jobsworth might not be capable of even understanding, let alone agreeing with, that argument - the concept of a regulation 'which does not apply' might be contrary to his religion!

Kind Regards, John

 

[scousespark]

In my opinion, the reg has no ambiguity and the commas make it's requiremnt quite clear. In John's first post he stated it as an either or scenario. I don't know what is inside a meter, but asuming that there are insulating parts inside would make bonding after the meter an understanable proposition.

I am a bit confused by John's quote
'Are you not overlooking the (one and only) reason for main bonding - namely to prevent a PD arising within the house by virtue of a difference in potential between the house's MET and the potential introduced (from outside the premises) by an incoming service pipe?'

There is an article in Wiring Matters from Summer 2012 which may be useful reading about this subject.