Earth bonding,...required or not?

[Adam_151]

Then we get to the question of given the scenero of a building internally piped fully in copper, but where the incomming cold water service is plastic, can the point be made that it might be sound engineering practice for a bond still to be made at the copper immediatly after the stop tap, in order that the internal pipework is effectivly earthed, even though it doesn't require to be bonded. I'm sure its been brought up here before in terms of faults to the pipework. But what about where you have a bathroom, and the pipework is extranous from the POV of the bathroom, and you wish to ommit suppliementy bonding, there is a requirement that such pipework is effectly connected to the buildings MET...

(putting aside the fact that this requirement can be effectly met when the installation is carried out and the scuppered by a plumber inserting a plastic push fit tee into the water pipework...)

 

[EFLImpudence]

NO.

That is completely misunderstanding just about everything.

 

[EFLImpudence]

Then we get to the question of given the scenero of a building internally piped fully in copper, but where the incomming cold water service is plastic,

Therefore none of the copper is an Extraneous-conductive-part so none of the main bonding requirements apply.

can the point be made that it might be sound engineering practice for a bond still to be made at the copper immediatly after the stop tap, in order that the internal pipework is effectivly earthed, even though it doesn't require to be bonded. I'm sure its been brought up here before in terms of faults to the pipework.

NO. It does not have to be effectively earthed. It is not an Exposed-conductive-part either.
(incidentally stop taps are mentioned nowhere in the regulations)

But what about where you have a bathroom, and the pipework is extranous from the POV of the bathroom, and you wish to ommit suppliementy bonding, there is a requirement that such pipework is effectly connected to the buildings MET...

That does not mean main bonding where not required.
It merely means satisfying the requirement of 415.2.2 as the note below 710.415.2 explains.

(putting aside the fact that this requirement can be effectly met when the installation is carried out and the scuppered by a plumber inserting a plastic push fit tee into the water pipework...)

No. the fitting of plastic parts may make the situation better by isolating some metal pipework so that it is no longer an Extraneous-c-p.

It would be better still if, instead of these misunderstood bonding requirements, pipework was isolated by various plastic parts.
It can't be done for gas pipes, but all the others could be.

 

[AndyPRK]

It would be nice to have a sticky on certain scenarios of where bonding is and isn't required.
And under what edition regulations.

or course that would require agreement

 

[JohnW2]

It would be nice to have a sticky on certain scenarios of where bonding is and isn't required.
And under what edition regulations.

In terms of main boding, the situation is very very simple ....

... if a conductive (i.e. metal) part (usually a utility supply pipe, occasionally structural metal - but rarely in domestic premises) enters a property and is such that it does (or could) provide a path to true earth (which, in practice, means that some of its path is underground), then it must have main bonding (to the MET) attached as close as practicable to the point of entry into the building. That's it. Nothing else.

Under current and recent regs, supplementary bonding is also very simple. It is only ever required in bathrooms, and the 'exceptions' are such that it is probably only rarely required even in bathrooms that other otherwise compliant with regs.

Moving from bonding to earthing, there is never a requirement to earth any metal pipes, per se. In practice, in premises with metal plumbing, much/most of the pipework (both water and gas) will be 'incidentally' earthed, by virtue of electrical continuity with boilers, CH pumps and motorised valves, immersions etc.

Kind Regards, John

 

[Adam_151]

That does not mean main bonding where not required.
It merely means satisfying the requirement of 415.2.2 as the note below 710.415.2 explains.

You are quite right that it doesn't mean you have to put a main bond in where it is not otherwise required, but by doing so it may allow you to met the test in 415.2.2 that you may not otherwise meet, of course you may meet that anyway, but you may not. My point was along the lines of, 'be careful what you omit because its not strictly necessary - it might have some effect elsewhere that you'd not considered'

 

[EFLImpudence]

So might earthing parts that do not require it (the proverbial spoon or door handle).

 

[Adam_151]

Unlikely, that would be rather silly... although I could send you the pictures I have somewhere of a suplimenatry bond to a pair of disabled grab rails in a toilet in a local authority building!

 

[JohnW2]

You are quite right that it doesn't mean you have to put a main bond in where it is not otherwise required, but by doing so it may allow you to met the test in 415.2.2 that you may not otherwise meet, of course you may meet that anyway, but you may not.

It's quite hard to think of situations, in practice, in which the requirement of 415.2.2 would not be met, even when there were no main bonding (because it was not required - e.g. in a house without gas that was fed by a plastic water pipe).

The point is that when (per 415.2.2) one measures resistance between exposed-c-ps and (things that might be) extraneous-c-ps, in practice one will get one of two answers - either 'very low resistance' or 'very high resistance'. In the latter case, the part is, by definition, not an extraneous-c-p (so 415.2.2 does not apply), whilst in the former case, 415.2.2 is satisfied.

My point was along the lines of, 'be careful what you omit because its not strictly necessary - it might have some effect elsewhere that you'd not considered'

It's a bit more complicated than that, since to 'unnecessarily' connect something to earth actually introduces an unnecessary hazard.

Kind Regards, John

 

[EFLImpudence]

There are also the bits of the regulations that people always disregard - possibly because of diagrams showing everything in a bathroom bonded together - like ignoring the E-c-p part of 4113.1.2.

710.415.2 "... according to 415.2 ..."

Exposed-c-ps and Extraneous-c-ps - are they in fact 'simultaneously accessible'?

Does your electric shower, in fact, have any Exposed-c-ps?

 

[EFLImpudence]

Unlikely, that would be rather silly... although I could send you the pictures I have somewhere of a suplimenatry bond to a pair of disabled grab rails in a toilet in a local authority building!

It's silly but you have an example.

 

[JohnW2]

Exposed-c-ps and Extraneous-c-ps - are they in fact 'simultaneously accessible'? ... Does your electric shower, in fact, have any Exposed-c-ps?

Indeed, and that also seems to go overlooked.

I can't think of any exposed-c-p's in any of my bathrooms, other than a brass shaver socket in one of them. In most bathrooms, the only exposed-c-ps are likely to be metal shaver sockets and light switches and, sometimes, electrical-heated towel rails and, sometimes, things like electric (e.g. oil-filled) heaters - and, even with them, they will often not be simultaneously touchable with any extraneous-c-ps.

Kind Regards, John

 

[bri160356]

OP here, many thanks for the replies guys;...very interesting and very much appreciated ,...even if some of the technical stuff about regs and extraneous c-ps etc proved a bit too much for my simple brain.

However, given the info that I’ve already posted, am I now safe to assume that my daughter will not need the extra earth bonding cable if she has her consumer unit replaced?

Fitting such a cable would no doubt entail a deal of disruption and some considerable expense,...which she is keen to avoid.

 

[EFLImpudence]

Plastic incoming pipes do not require bonding and indeed cannot be bonded.
The internal pipework does not need it either.

So, from the information given, no more main bonding is required.

 

[AndyPRK]

I love the imagination in the comments to this video