Current Earth Bonding Regulations

[JohnW2]

Does that not come under "Main Bonding correctly applied"?

I don't think so - or, at least, that's never how I've read the regs. The preamble to points (iv), (v) and (vi) of 701.415.2 says that supplementary bonding may be omitted if there is is "Main Bonding in accordance with 411.3.1.2" (and those other three conditions were satisified) - and I would take that to correspond to your "Main Bonding correctly applied".

However, 701.415.2(vi) then goes on to also require that all extraneous-c-ps in the bathroom are 'effectively connected' to that Main Bonding. This will obviously normally be the situation, via the pipework, but I had always taken it to mean that there had to be a demonstrated 'adequately low' (goodness knows!) resistance from the extraneous-c-ps in bathroom to the MPB/MET - i.e. to rule out the possibility of some 'too high resistance' (whatever that means) connections somewhere in the pipework. What did you interpret (vi) as meaning?

Kind Regards, John

 

[EFLImpudence]

Does that not come under "Main Bonding correctly applied"?

I don't think so - or, at least, that's never how I've read the regs. The preamble to points (iv), (v) and (vi) of 701.415.2 says that supplementary bonding may be omitted if there is is "Main Bonding in accordance with 411.3.1.2" (and those other three conditions were satisified) - and I would take that to correspond to your "Main Bonding correctly applied".
However, 701.415.2(vi) then goes on to also require that all extraneous-c-ps in the bathroom are 'effectively connected' to that Main Bonding. This will obviously normally be the situation, via the pipework, but I had always taken it to mean that there had to be a demonstrated 'adequately low' (goodness knows!) resistance from the extraneous-c-ps in bathroom to the MPB/MET - i.e. to rule out the possibility of some 'too high resistance' (whatever that means) connections somewhere in the pipework. What did you interpret (vi) as meaning?

More confusion, it would appear, with the preamble being similar to 701.415.2(vi) in that 411.3.1.2, mentioned in both, must be met to ensure the main bonding is correctly applied.
411.3.1.2 being the correct installation of main bonding.

The note below 701.415.2 states this effective connection can be assessed by the application of 415.2 which in turn states that this is assessed by fulfilling 50/Ia.
As in the case of an RCD (which is why we are determining it) this is 50/0.03 - 1,666Ω - as you say, it would be difficult to imagine it would not be met.

I cannot think of an extraneous-c-p for the bathroom where this would not be the case, can you?
Therefore, I have presumed that as long as 411.3.1.2 is met so would 701.415.2(vi)

 

[westie101]

Only main bonding and if you have plastic incoming water pipe then dont bond that either.

If it becomes metallic in the house and the supply is TNCS that is incorrect and the DNO if they found out could disconnect the supply on safety grounds.

Don't all forget, either, the need to maintain the Farady cage effect to cover for a lost neutral/earth on the TNCS supply

 

[JohnW2]

If it becomes metallic in the house and the supply is TNCS that is incorrect and the DNO if they found out could disconnect the supply on safety grounds. ... Don't all forget, either, the need to maintain the Farady cage effect to cover for a lost neutral/earth on the TNCS supply

That doesn't make sense to me. If the pipe only becomes metal within the house, and if no metal enters the house, then all of the metal pipework is within that Faraday cage. Even BS7671 only requires main bonding of conductors which are "liable to introduce a potential (usually earth potential)" from outside of the house (Faraday cage) - and if the only pipe which enters the house from outside is plastic, that can't happen, even if there is metal pipework within the house. You're surely not saying that DNOs require all metal pipes within a building to be main bonded, even if they are electrically isolated from the outside world?

Can you explain?

Kind Regards, John

 

[JohnW2]

More confusion, it would appear, ... I cannot think of an extraneous-c-p for the bathroom where this would not be the case, can you? Therefore, I have presumed that as long as 411.3.1.2 is met so would 701.415.2(vi)

As I said, giving the underlying requirement that main binding be 'present and correct', I have always taken 701.415.2(vi) to be talking about the possibility of their being an inadequately low resistance path (whatever limit one may chose) through the pipework from the bathroom to the MPB/MET - maybe due to a series of corroded compression fittings or something like that. It just seems to me that requiring the MPB to be 'present and correct' and requiring that the extraneous-c-ps in the bathroom are 'effectively connected' to that MPB are probably intended as two different considerations/ requirements (if not, why 'require' both?).

Kind Regards, John

 

[vards01]

So are we still in agreement that if the water and gas are properly bonded to the consumer unit this installation does not require supplementary bonding?

Or are we now saying all copper pipes in the bathroom need to be bonded?

 

[JohnW2]

So are we still in agreement that if the water and gas are properly bonded to the consumer unit this installation does not require supplementary bonding?

Provided that the other conditions mentioned by EFLI were also satisfied (which they probably will be), yes.

Or are we now saying all copper pipes in the bathroom need to be bonded?

None of us have suggested that, but I haven't yet really got a clue as to what westie was recently suggesting - hopefully he will clarify soon!

Kind Regards, John

 

[vards01]

I just wanted to be sure before the inspection takes place, as I've spent an age getting it all finished to a good standard for rental and didn't want anything broken or damaged to fit bonding connectors........

 

[EFLImpudence]

It just seems to me that requiring the MPB to be 'present and correct' and requiring that the extraneous-c-ps in the bathroom are 'effectively connected' to that MPB are probably intended as two different considerations/ requirements (if not, why 'require' both?).

Yes, I think you are right.

So, any parts which are between 1,666 and 23,000Ω should still be bonded.

 

[JohnW2]

It just seems to me that requiring the MPB to be 'present and correct' and requiring that the extraneous-c-ps in the bathroom are 'effectively connected' to that MPB are probably intended as two different considerations/ requirements (if not, why 'require' both?).

Yes, I think you are right. ... So, any parts which are between 1,666 and 23,000Ω should still be bonded.

Maybe. Certainly parts with a resistance to the MET between some two figures - maybe those figures (as we've discussed before). I guess it depends on whether <1666&#937; satisfies the requirement in the reg we're discussing that there be an 'effective connection'. I think I would personally be concerned if the resistance (of what was meant to be continuous copper pipework) was much more than 'a few ohms' (and certainly if it were 'hundreds of ohms') - since that would suggest to me that 'something was going on' which could get worse.

Kind Regards, John

 

[EFLImpudence]

Yes, true - but the figures are just nominal ones as has been discussed before.

 

[JohnW2]

Yes, true - but the figures are just nominal ones as has been discussed before.

Indeed - but, as I said, if the resistance of what was meant to be a continuous run of copper pipe was hundreds, or even dozens, of ohms, I would be very concerned - so I think the mental 'rule of thumb' I would personally work to would probably be a lot lower than 1666&#937;.

Kind Regards, John

 

[EFLImpudence]

Yes, I know but that is 50/Ia.

What else can be used?

 

[JohnW2]

Yes, I know but that is 50/Ia. What else can be used?

I've sort-of answered that (albeit not numerically) in terms of common-sense considerations of what one would expect the resistance of a handful of metres of copper pipe to be. If it were more than a small number of ohms, I would suspect that some process (e.g. corrosion of joints) was at work which could easily (and perhaps quite rapidly) get much worse.

Would you really be happy to regard the bathroom pipework as being 'effectively connected to the MPB' (and reasonably confident that such would remain the case) if you measured a resistance of 1000&#937; or 1500&#937;?

Kind Regards, John

 

[EFLImpudence]

It could be a plastic joint with the resistance of the water being measured.

Easier to bond the 'offending' pipe than hunt for the cause.