Earthing... yes another thread

[JohnW2]

I do see the point. I assume you mean extraneous to the bathroom? There is a possibility that a potential could exist between different services / pipes such a cold pipe from the rising main, hot pipe from the cylinder and CH pipes from the boiler. Supplementary bonding these can only be a good thing IMO.

Then it would be required.

What do you mean by 'then'? Do you mean if "effective connection" to the main bonding could not be established to satisfy the regs?

Kind Regards, John.

 

[EFLImpudence]

I do see the point. I assume you mean extraneous to the bathroom? There is a possibility that a potential could exist between different services / pipes such a cold pipe from the rising main, hot pipe from the cylinder and CH pipes from the boiler. Supplementary bonding these can only be a good thing IMO.

Then it would be required.

What do you mean by 'then'? Do you mean if "effective connection" to the main bonding could not be established to satisfy the regs?.

Well, if the possibilities of a potential which RF mentions exist then it (supplementary bonding) would be required.

I did not see this as a reply to your post about when s.b. was not required.

I am not quite sure how 'possibilities' are determined but if that is the case then s.b. would be required.

 

[JohnW2]

Well, if the possibilities of a potential which RF mentions exist then it (supplementary bonding) would be required. I did not see this as a reply to your post about when s.b. was not required. I am not quite sure how 'possibilities' are determined but if that is the case then s.b. would be required.

Quite. I presumed he was talking about some hypothetical possibilty that PDs could exist between different pipes entering a bathroom. However, I think he may have missed the point I eluded to - that in order to satisfy the reg's conditions for omiting supplementary bonding in a bathroom, all pipes entering the bathroom must be 'effectively connected' to the installation's main protective equipotential bonding. If that condition is satisfied, then I don't think the possibility to which he referred is possible If the condition is not satisfied, the regs then obviously call for supplementary bonding, anyway.

Kind Regards, John.

 

[bernardgreen]

I can see where most people are coming from in this discussion. Satisfying the regulations at the time of installation and certification is necessary.
But as EFLImpudance said

I don't think the regulations tend to cater for the 'vic's when less improbable situations occur.

some of the possible fault scenarios have been ignored or dismissed by the "regulations". Unfortunately when they do occur they can be fatally serious for the people involved. I am often reminded ( in various activities ) about the expression the person died but it is OK for us as we followed the rules . In almost all cases the rule book is changed but then too late for the deceased. Seldom is any action taken against the ( negligent ? ) people who wrote the rules.

but this just shows that thinking of a particular happening which seems to throw doubt on the regulations is not a reason for doing the opposite.

But it could be a reason for doing something that the rules consider is unnecessary due to the vanishly small chance that it could happen some tim,e after the installation has been certified as compliant.

I accept the rules cannot cater for the idiots in this world other than by imposing a total ban on anything that can be a hazard when in the hands of a fool. ( such as banning private cars ) But they do need to allow common sense ( and basic electrical theory ) to be used along side the regulations to try to ensure long term safety of the system and not just compliance on the day of certification.

 

[ban-all-sheds]

If your wet nail touches the bath it would be good for the bath to be (effectively) earthed.

If your wet nail touches someone's foot and they touch the bath it would be good for it to not be.

On balance, if your bath is not part of the electrical installation, in the same way that your door handles, toothbrush holder, coat hooks etc are not then IMO you'd be mad to make it so.

 

[JohnW2]

... some of the possible fault scenarios have been ignored or dismissed by the "regulations". Unfortunately when they do occur they can be fatally serious for the people involved. ... But it could be a reason for doing something that the rules consider is unnecessary due to the vanishly small chance that it could happen some tim,e after the installation has been certified as compliant.

I think we all agree that there are shortcomings in the regs, that those regs have to 'draw the line' somewhere in relation to very unlikely scenarios and that people are (as they should be) free to take safety measures over and above the minimum required by the regs, particularly if they are not comfortable with where the regs have drawn that line.

However, this discussion is a little more complicated. As some people always say in these threads (e.g. BAS's lastest post), it's not simply a case of going beyond the safety standards required by the regs. The 'additional measures' (beyond those required by the regs) being discussed have the effect of decreasing safety in some very unlikley scenarios, just as they have the effect of increasing safety in some other very unlikely scenarios. A judgment therefore has to be made, which makes it almost inevitable that different people will come to different conclusions.

Kind Regards, John.

 

[bernardgreen]

On balance, if your bath is not part of the electrical installation, in the same way that your door handles, toothbrush holder, coat hooks etc are not then IMO you'd be mad to make it so.

Most baths are part of the electrical installation as they have a connection via taps and pipe work to the "earth" which is often the incoming supply neutral. Even if the pipes are plastic there is water inside them in contact with the metal of the taps. Remember the requlations do insist on incoming water supplies being bonded to the MET even when the external supply is a "non conductive" plastic. Tghis bond is essential to prevent that non conductive pipe or the water inside it importing an external potential into the building. ( Distilled water is almost non conductive, tap water is conductive, how conductive depends on what natural and artificial additives are in the water )

 

[JohnW2]

Most baths are part of the electrical installation as they have a connection via taps and pipe work to the "earth" which is often the incoming supply neutral. ... Remember the requlations do insist on incoming water supplies being bonded to the MET ....

As far as I can see, provided that all required main protective equipotential bonding is in place, the sort of risks you are considering only exist if you start talking about 'damp walls' etc. In the absence of such factors, there is no 'true earth potential' within the building, and it therefore doesn't matter what potential the CPCs of the installtion, pipework, baths etc. have with respect to true earth - any accessible conductive material will either (usually most of it) be equipotential with MET, supply 'earth' etc. (hence also equipotenial will all other bonded or earthed conductive materials) OR else will be floating - in neither case presenting a hazard.

Kind Regards, John.

 

[ban-all-sheds]

Most baths are part of the electrical installation as they have a connection via taps and pipe work to the "earth" which is often the incoming supply neutral.

In which case it is an extraneous conductive part.

Even if the pipes are plastic there is water inside them in contact with the metal of the taps.

In which case, as long as the plastic section is >1m (IIRC) the taps are not extraneous-conductive-parts.

Remember the requlations do insist on incoming water supplies being bonded to the MET even when the external supply is a "non conductive" plastic.

For no sound scientific reason.

Tghis bond is essential to prevent that non conductive pipe or the water inside it importing an external potential into the building. ( Distilled water is almost non conductive, tap water is conductive, how conductive depends on what natural and artificial additives are in the water )

Tap water is pretty non-conductive too.

 

[JohnW2]

Remember the requlations do insist on incoming water supplies being bonded to the MET even when the external supply is a "non conductive" plastic.

For no sound scientific reason.

I'm not actually convinced that they do insist on it, in the case when a water service enters the premises in plastic. Although 544.1.2 says some potentially confusing things about the situation when there is an 'insulating section or insert' at the point where the supply enters the premises (or a meter), the whole of 554.1 relating to main protective bonding is really only invoked if there is a requirement under 411.3.1.2 for such bonding - and 411.3.1.2 talks explicity of extraneous-conductive-parts (with 'water installation pipes' in its 'includes' list). I reckon that, if water does enter the house in plastic, 411.3.1.2 does not (in accordance with scientific/engineering common sense) actually require any main bonding of water pipes, since its requirements relate only to bonding of extraneous-conductive-parts and, in that situation, there is no extraneous-conductive-part to bond.

Kind Regards, John.