18th 544.1.2

[JohnW2]

.... considering a standard domestic property housing one single family. This property has a single phase electrical suppy, a gas supply fed to the house by means of a yellow MDPE pipe into an outside meter cupboard and finally into the property itself. A water supply supplied via blue MDPE pipe to the inside stop valve which feeds a copper piped internal system. ....

From the point of view of the electrical regulations (BS7671) you need say no more than that. Provided only that the metal pipe from the external gas meter into the house does not go underground (or, maybe, go very close to the ground) neither the gas nor water supplies to that property require (or need) any 'main bonding' (Protective Equipotential Bonding') - it's as simple as that.

Electricity Regs - Non statutory in their own right but used as reference for 'Competent Persons' schemes.

True, but more than that - for the vast majority of people the only way in which they can demonstrate compliance with the relevant Statutory legislation (Part P of the Building Regs) is by complying with BS7671. Hence, for most people the Wiring Regulations (BS7671) are 'effectively Statutory'.

Kind Regards, John

 

[AlanE]

From the point of view of the electrical regulations (BS7671) you need say no more than that. Provided only that the metal pipe from the external gas meter into the house does not go underground (or, maybe, go very close to the ground) neither the gas nor water supplies to that property require (or need) any 'main bonding' (Protective Equipotential Bonding') - it's as simple as that.

Ok 'From electrical point of view alone that may, or maybe not correct.' At moment not going to say either way.

I have added a little more to the construction of the property which may ore maynot be of relevance.

 

[EFLImpudence]

Ok 'From electrical point of view alone that may, or maybe not correct.'

It is correct.

An electrical point of view is all that matters. It is electricity that is being considered.
That another utility may state otherwise - for whatever reason - does not alter how it works.

At moment not going to say either way.

It doesn't matter what you say; that won't alter how it works either.

 

[JohnW2]

Ok 'From electrical point of view alone that may, or maybe not correct.' At moment not going to say either way.

It's an electrical issue. What I wrote was correct in terms of electrical principles, electrical common sense and the Wiring Regulations (BS7671). In the situation you describe (with the one caveat I mentioned about the gas pipe) there is absolutely no need or point in installing main bonding. If some other people, 'authorities' or even legislation say otherwise, then either they are thinking about something other than the electrical installation within the property (goodness knows what) or they really do not know what they are talking about.

I have added a little more to the construction of the property which may ore maynot be of relevance.

None of that additional information makes the slightest difference to what I have written. The ONLY thing which creates a need for main bonding is a metal object (like a pipe) which has contact with 'the ground' entering the property.

Kind Regards, John

 

[AlanE]

2.

The Electricity Supply Regulations 1988 - (Statutory)

Protective multiple earthing

7.—(1) The supplier shall not connect or permit the connection of, or continue, a supply to any part of a consumer’s installation where the supply neutral conductor is, or is intended to be, used to connect any circuit protective conductor in that part of the consumer’s installation with earth unless he is satisfied so far as is reasonably practicable, that—

(a)his works comply with the requirements of paragraphs (2) or (3) and paragraphs (4) to (6); and

(b)the consumer’s installation complies with the requirements of paragraphs (7) to (10).

(2) (a) For the purposes of this paragraph and paragraph (3)—

(i)measurements shall, where appropriate, be made along the distributing main;

(ii)in a distributing main which is divided so that it has more than one end, apart from that at the source of voltage, each such end shall be treated as if it were the only end of that main.

(b)The supply neutral conductor shall be connected with earth at a point no nearer to the source of voltage than the junction of the distributing main with the service line connecting it with the consumer’s installation which both uses the supply neutral conductor as its connection with earth and is the nearest such installation to the end of the distributing main.

(3) (a) This paragraph applies only where—

(i)at least one of the consumer’s installations (not exceeding four in total) whose connections to a distributing main lie nearest to the end of the main uses the supply neutral conductor for the purpose of connecting the installation with earth; and

(ii)the distance of the furthest of those connections from the end of the distributing main does not exceed 40 metres.

(b)In any case where this paragraph applies the supply neutral conductor shall be connected with earth at a point no nearer to the source of voltage than the junction between the distributing main and the service line connecting the consumer’s installation referred to in sub-paragraph (a) above which is nearest to the source of voltage in the distributing main.

(4) The supply neutral conductor shall be connected with earth at such points as may be necessary to ensure that the resistance to earth of the supply neutral conductor—

(a)does not anywhere exceed 20 ohms; and

(b)is such that the fuses or automatic switching devices protecting the high voltage side of any transformer will operate if any fault in it causes the low voltage side to become charged at a higher voltage unless the high voltage side of that transformer is connected with earth through a continuously rated arc suppression coil.

(5) The supply neutral conductor shall have a copper equivalent cross-sectional area which satisfies the requirements of regulation 6.

(6) Any connection with earth required by this regulation may be made by connecting the supply neutral conductor to the supply neutral conductor of another distributing main.

(7) Any metalwork on the consumer’s premises which—

(a)is in, or may reasonably be expected to come into electrical contact with earth;

and

(b)is so situated that any person, livestock or domestic animal could simultaneously touch—

(i)any such metalwork, or any metalwork in electrical contact therewith; and

(ii)any exposed metalwork forming part of the consumer’s installation but not normally carrying an electric current, or any metalwork in electrical contact therewith,

shall be connected to the earthing terminal.

 

[JohnW2]

The Electricity Supply Regulations 1988 - (Statutory)
...... (7) Any metalwork on the consumer’s premises which—
(a)is in, or may reasonably be expected to come into electrical contact with earth; and ... shall be connected to the earthing terminal.

... which is exactly what EFLI and myself have told you more times than I can remember - bonding of something metal (like an incoming utiulity pipe) to the MET is required IF (and ONLY IF) "it is in, or may reasonably be expected to come into electrical contact with earth". That means that (in accordance with electrical common sense, as well as BS7671 and the regulations you quote) the incoming gas and water pipes in the property you recently described would not need bonding (unless the gas pipe entering the property comes in contact with the ground anywhere).

... and, by the way, although the regulation you quoted related specifically to PME, exactly the same also applies (in relation to bonding) with any earthing system.

Kind Regards,
John

 

[AlanE]

So gas pipes and water pipes comming in contact with earth don't count only those comming in contact with the physical earth outside the property?

So heating sytem pipes, and water pipes, cannot be classed as extraneous metal conductors?

 

[JohnW2]

So gas pipes and water pipes comming in contact with earth don't count only those comming in contact with the physical earth outside the property?

If I understand your correctly, that's exactly right - to be extraneous-conductive-parts (which need main bonding) they have to come into contact with the 'actual earth' ('ground', soil or whatever) (or in contact with some other metal which itself is somewhere in contact with 'actual earth') somewhere (outside or underneath the property). Metal pipes within the property which are 'in contact with' the 'earthing system' of the property's electrical installation (which they nearly always be in an all-copper plumbing system - because boilers, CH pumps/valves, immersions etc. will all be connected to that earthing system) do NOT qualifty as extraneous-conductive parts (and therefore don't require main bonding)

So heating sytem pipes, and water pipes, cannot be classed as extraneous metal conductors?

Exactly - provided that they don't come into contact with 'the actual earth' - outside of or beneath the property.

Maybe you are at last coming to understand what main bonding is all about.

The whole point of main bonding ('PEB') is that, without it (when needed) there is a risk that under certain fault conditions, there could be a dangerous potential difference between the electrical installation's earthing system (hence the metal cases of many electrical appliances, and pipes/radiators etc. if there is metal plumbing) and 'true earth' - so someone simultaneously touching one of those and an incoming pipe which was connected to 'true earth' could be at serious risk. By bonding any pipes 'coming out of the ground' to the electrical system's earth, one minimises the difference in potential which can exist between them.

Kind Regards, John

 

[EFLImpudence]

I think what is confusing you is the term 'earth' in the text.

It means 'The Earth' - the ground.

Where any parts are connected to 'earth' solely by the 'earthing' system of the installation, because of their contact with an appliance CPC, they are obviously already connected to the 'earthing' terminal.

It could be argued that parts so connected do not actually require Main Bonding even when they are also connected to 'The Earth' - electrically it does not matter where the Main Bonding is connected - but the regulations state that Main Bonding shall be applied at the point of entry to the premises to negate alterations to the pipework disconnecting the extraneous-c-p from its earthing conductor. Plus - there is a minimum size for the Main Bonding conductors and CPCs do not meet this requirement.

 

[JohnW2]

It could be argued that parts so connected do not actually require Main Bonding when they are also connected to 'The Earth' - electrically it does not matter where the Main Bonding is connected - but the regulations state that Main Bonding shall be applied at the point of entry to the premises to negate alterations to the pipework disconnecting the extraneous-c-p from its earthing conductor. Plus - there is a minimum size for the Main Bonding conductors and CPCs do not meet this requirement.

Indeed.

I would say that the argument that it doesn't really matter where one attaches a bonding conductor still applies to gas pipes (which are necessarily all metal), as it did in the days when all water and CH systems exclusively used metal pipework - since the pipework itself will create an electrical path throughout all the pipework which is at least as good as a ' bonding conductor would. However, now there is a risk that bits of plastic pipe and/or plastic fittings will be put into water (even CH) systems, the only safe place to bond an incoming water pipe (if bonding is needed) is at (or near) the point of entry.

However, as you go on to say, arguing that pipes which are 'connected to earth' via CPCs (and which are also extraneous-c-ps, hence connected to 'The Earth') has never been particularly safe for either gas or water pipes (at least, not since the advent of TN-C-S). As you say, there is a minimum size required for a main bonding conductor, and that is because the very high currents that could arise under some fault conditions (particularly with TN-C-S) could melt CPCs.

I realise that you know all this, but I am writing it primarily for the benefit of Alan (and any 'lurkers').

Kind Regards, John

 

[EFLImpudence]

Yes, I started out by just intending to show that where the only contact with earth was a CPC then -

"(7) Any metalwork on the consumer’s premises which—
(a)is in, or may reasonably be expected to come into electrical contact with earth;
shall be connected to the earthing terminal."

already was (connected to the earthing terminal).

Then I thought I'd add ... and then to explain that ... etc.

 

[AlanE]

Maybe you are at last coming to understand what main bonding is all about.

Or comming to understand your logic bou not conceeding that logic is correct.

 

[AlanE]

You cite the situation of gas meters and the material that the actual suppy pipe is made of.

This was, at one time, of metal construction. But an insulating fitting was fitted between the pipe itself and the emergency isolation off valve. This would then mean that the actual pipe was electrically isolated from the meter itself. Follows therefore that no current can flow from the property back to the ground earth. There has NEVER been a requirement to bond this actual pipe anywhere always as near as possible to point of entry. So how does your logic involve this service pipe material in any way? MDPE service pipe has been used for probably around 20 years or so for gas I would have thought.

Two normal outside mounting points for gas meters, in a wall cabinet or semi submerged. The latter has a special meter that is designed to sit in a pool of water and this is often the case to find it so.

 

[JohnW2]

Or comming to understand your logic bou not conceeding that logic is correct.

It's not "my logic", it's just electrical/Physics facts (and common sense), the understanding of which is probably within the capabilities of anyone with a reasonable GCSE in Physics, and certainly those with A-Level Physics.

Kind Regards, John

 

[EFLImpudence]

You cite the situation of gas meters and the material that the actual suppy pipe is made of.

This was, at one time, of metal construction. But an insulating fitting was fitted between the pipe itself and the emergency isolation off valve. This would then mean that the actual pipe was electrically isolated from the meter itself. Follows therefore that no current can flow from the property back to the ground earth. There has NEVER been a requirement to bond this actual pipe anywhere always as near as possible to point of entry.would have thought.

Yes there has. It is and always has been an extraneous-conductive-part if it enters the premises.

The regulation to bond on the consumer's side of an internal meter is the regulation that I have been saying has been wrong for years and has just now been corrected.

So how does your logic involve this service pipe material in any way? MDPE service pipe has been used for probably around 20 years or so for gas

MDPE does not conduct electricity and therefore cannot be an extraneous-c-p. Metal does and therefore can.

Two normal outside mounting points for gas meters, in a wall cabinet or semi submerged. The latter has a special meter that is designed to sit in a pool of water and this is often the case to find it so.

So?