Gas pipe bond (IET vs Corgi)

[Malc]

Are the corgi regs different to IET regs on gas pipe bonding? IET says as pipe comes in to building and where practical within 600mm. No mention of visible.

In the house I'm building I was planning to have the meter box as in the ground type at the front. Gas pipe comes in and up the wall to floor void. Then along floor void splitting off to boiler and hob. Up the wall run is buried in plaster (corner of room) so nearest bond point in in floor void, ~2.4m in but IET does say "where practical" and bonding is a bit optional since gas main will be plastic (but copper from my side of meter I expect). I suppose it might be possible to view the bond in floor void (it would be under a bath so could have a hatch) but real visible places would be at boiler and hob so hardly bonded as it comes in.

 

[securespark]

Any reason why not in the meter box?

Is the ground floor suspended?

 

[EFLImpudence]

Are the corgi regs different to IET regs on gas pipe bonding? IET says as pipe comes in to building and where practical within 600mm. No mention of visible.

Not quite right - "...at entry point where practicable".
"Where practicable" means where it would achieve the same result.

In the regulations, the 600mm. only applies to internal meters and is in any case WRONG.


If your supply pipe is plastic then it does not require bonding as it is not an extraneous-conductive-part.

 

[Taylortwocities]

Has anybody seen a plastic gas pipe run to a house? I believe that they use plastic as the main service pipes in the street, but I think that the final pipe run is copper with a plastic serving.

Anybody confirm/deny? Thanks..

 

[Malc]

According to onsite guide the wording is

"All main bonding connections are to be applied to the consumer's side of any meter, main stop valve or insulating insert and, where practicable, within 600mm of meter outlet union or point of entry into the building if the meter is external"

So since I'm coming in at just above ground floor level (solid floor BTW) near practicable point is in 1st floor void, which is not visible which I've seen quoted. Where practical does not mean where it would achieve the same result. That would be "or an equivalent point" or some such. It means where it can be realistically done. Impedance wise there is little difference if I bond in the floor void, especially if I bond before any joint so I'm on the straight pipe up the wall.

Although I will have a plastic gas main, the meter pipe will likely be copper so I do have a metallic conductor entering the house so it should be bonded, even though it is only a few inches of pipe. It's allowed not to bond where the incoming pipe is plastic, which I read as saying the plastic pipe must come into the house and there be an internal meter.

 

[Newboy]

Internal plastic pipe for gas is not permitted.

Additionally where the pipework is enclosed in a void, the void must be vented.

PS CORGI ceased to exist as the official registration scheme in March 2009 (2010 in Northern Ireland)

 

[Malc]

Gas network use plastic which goes to meter box. Gas supplier (them who send the bills) fits meter to plastic pipe end (maybe copper there?). Your fitter runs pipe from meter into house for boiler, hob, fire etc.. That last run is most certainly in copper AFAIK.

 

[Malc]

Internal plastic pipe for gas is not permitted.

Additionally where the pipework is enclosed in a void, the void must be vented.

PS CORGI ceased to exist as the official registration scheme in March 2009 (2010 in Northern Ireland)

Useful to know. My vertical pipe up the inside wall will be on a dot and dab wall so will have a solid dab from floor to ceiling. Pipe surround will vent to floor void.

But is there anything in gas regs to say bonding has to be visible?

 

[JohnW2]

Has anybody seen a plastic gas pipe run to a house? I believe that they use plastic as the main service pipes in the street, but I think that the final pipe run is copper with a plastic serving.

As has been said, my understanding is that plastic pipe is not allowed within buildings (at least domestic ones, probably all).

However, if the meter is external, a reasonable distance off the ground and supplied with plastic pipe then, as EFLI has said, any metal pipe entering the building from the consumer's side of the meter will not be an extraneous-c-p, and will therefore not need any main bonding at all.

Kind Regards, John

 

[JohnW2]

But is there anything in gas regs to say bonding has to be visible?

I can't tell you about the gas regs, although one would probably expect there to be a requirement for the connection to be 'available for inspection', in order that it can be verified that it is present and satisfactory.

In any event, the electrical regs require that (with few exceptions) any joint (and I think one can assume that includes a joint between a cable and a pipe) has to be accessible for inspection, maintenance and testing.

Kind Regards, John

 

[EFLImpudence]

According to onsite guide the wording is

"All main bonding connections are to be applied to the consumer's side of any meter, main stop valve or insulating insert and, where practicable, within 600mm of meter outlet union or point of entry into the building if the meter is external"

The actual regulation says - and only applies to extraneous-conductive-parts:
The main protective bonding connection to any gas, water or other service shall be made as near as practicable to the point of entry of that service into the premises.
Where there is an insulating section or insert at that point, or there is a meter, the connection shall be made to the consumer's hard metal pipework and before any branch pipe work.
Where practicable the connections shall be made within 600mm. of the meter outlet union OR at the point of entry to the building if the meter is external.

So since I'm coming in at just above ground floor level (solid floor BTW) near practicable point is in 1st floor void, which is not visible which I've seen quoted. Where practical does not mean where it would achieve the same result. That would be "or an equivalent point" or some such. It means where it can be realistically done.

Is that therefore not achieving the same result?
There would be little point bonding it somewhere that did not achieve the desired result - like above, for example, after an insulating section.

Impedance wise there is little difference if I bond in the floor void, especially if I bond before any joint so I'm on the straight pipe up the wall.

True.

Although I will have a plastic gas main, the meter pipe will likely be copper so I do have a metallic conductor entering the house so it should be bonded, even though it is only a few inches of pipe.

It will therefore (if the pipe emerging from the ground is plastic) NOT be an extraneous-c-p and does not require bonding.

It's allowed not to bond where the incoming pipe is plastic, which I read as saying the plastic pipe must come into the house and there be an internal meter.

It's allowed (and advisable) not to bond parts which are not extraneous-c-ps no matter where they are.

 

[Malc]

Since my gas meter box is a buried in the ground type I think the copper pipe to the house would be a be too close to ground level not to bond it. A meter box half way up the wall would be different but one on the floor might fill up with water in extreme circumstances.

You're right about the need to inspect all joints, I'd forgotten that. I'm not sure how that rule applies to bonding of radiators in bathrooms where typically these are bonded out of sight. I suppose a solution would be to allow for testing of the remote connection. That is labelling the earth connection at the CU, e.g. gas incoming, so for inspection you could remove that and then measure the resistance down that cable to the gas pipe to earth that you added to gas pipe. Same for bathroom radiator bonding (which you need if you have plastic CH pipework). I would suspect though that an inspection would be satisfied with just measuring that the gas pipe, bathroom radiators, etc. are just connected to earth rather than proving a particular cable. The gas pipe is likely to have 2 connections, the bonding and the boiler earth so that's the only one where there could be doubt as to the bond connection at the incoming pipe.

 

[EFLImpudence]

Since my gas meter box is a buried in the ground type I think the copper pipe to the house would be a be too close to ground level not to bond it. A meter box half way up the wall would be different but one on the floor might fill up with water in extreme circumstances.

A drain hole may be easier.

I'm not sure how that rule applies to bonding of radiators in bathrooms where typically these are bonded out of sight.

Radiators do not require bonding.
The pipes supplying them might and this may be done anywhere which achieves the desired result, i.e. a low enough impedance between them.

I suppose a solution would be to allow for testing of the remote connection. That is labelling the earth connection at the CU, e.g. gas incoming, so for inspection you could remove that and then measure the resistance down that cable to the gas pipe to earth that you added to gas pipe.

Yes, we do that. It's a bond that we added; not an earth.

Same for bathroom radiator bonding (which you need if you have plastic CH pipework).

If you have plastic pipework then NO supplementary bonding would be necessary.
It is not possible for plastic pipe, nor an isolated radiator, to introduce any potential into the bathroom.

I would suspect though that an inspection would be satisfied with just measuring that the gas pipe, bathroom radiators, etc. are just connected to earth rather than proving a particular cable.

The point about Supplementary Bonding in bathrooms is that it connects together the parts in the bathroom. They do not have to be connected to the Main Earthing Terminal or Consumer Unit.
If they were not already connected to earth in some way then they would not require bonding (together).

The gas pipe is likely to have 2 connections, the bonding and the boiler earth so that's the only one where there could be doubt as to the bond connection at the incoming pipe.

Not sure what exactly you mean.
It is not possible to determine for certain that the gas pipe is NOT an extraneous-c-p while it is connected to the boiler or similar things, but then, as it is connected to them, bonding it unnecessarily will not introduce a hazard.

 

[Malc]

I would imagine a meter box has a drain hole but that might be worse as with saturated ground that could introduce water.

Supplementary bonding has to connect all exposed metalwork and the water pipes for it to be effective. Otherwise a fault raising the voltage on one item would raise it on all others and water would still likely be earthy. With plastic water pipes it seems safer to also "earth" the supplementary bonding (I'm assuming the water has been bonded as it enters the house) to ensure that the metal potential is same as the water.

Radiators I didn't explain very well. In the past I've fitted towel rail types with chrome pipes going down through the floor to connect to the CH pipework, some of which is plastic so it can't be certain there is a conductive path back to "earth". As metal pipes are going through the floor this makes the radiator an extraneous metallic part so needs protective bonding.

I didn't explain my reasoning on the gas pipe very well either. What I am thinking is the case of a regular wiring check. How can you tell if the gas pipe still has a bond? My solution is to have the bond wire labelled as gas pipe bond at the CU. To test remove this and measure impedance to E terminal. If necessary connect E to gas pipe but I think that will be happening anyway due to boiler. The same can be done for bathroom bonding but then you might need to connect to E the parts in the bathroom if you have plastic pipe in CH as they won't have a path then.

 

[JohnW2]

Supplementary bonding has to connect all exposed metalwork and the water pipes for it to be effective.

It only has to connect exposed metalwork (and exposed-c-p of electrical items) if they are extraneous-conductive-parts. To unnecessarily connect metal work to earth (in the name of bonmding), increases, rather than decreases, hazards,

Radiators I didn't explain very well. As metal pipes are going through the floor this makes the radiator an extraneous metallic part so needs protective bonding.

Those pipes are only extraneous-c-ps if they are 'liable to introduce a potential'.

What I am thinking is the case of a regular wiring check. How can you tell if the gas pipe still has a bond?

This is one reason why the bonding to the gas pipe needs to be accessible for inspection. AS for testing it, about the only thing one can really do is to disconnect the bonding cable from the pipe (which obviously requires that connection to be 'accessible') and measure the resistance of that cable back to the Main Earthing Terminal (MET) at/near the CU ... which I think is probably what you are going on to say .....

My solution is to have the bond wire labelled as gas pipe bond at the CU. To test remove this and measure impedance to E terminal. If necessary connect E to gas pipe but I think that will be happening anyway due to boiler.

There is generally a requirement to bond the incoming gas pipe to the MET of the installation, regardless of other ways in which it may be connected to 'earth'.

Main bonding is not really anything to do with 'earth', per se. The whole idea is to ensure that all touchable metal (e.g. pipes) in the building are at the same potential as the protective conductors of the electrical installation - i.e. as connected to the MET at/near the CU. That potential may or may not be the potential of true earth. It is because extraneous-c-ps like incoming service pipes may try to introduce true earth potential that one needs the main bonding - to, if necessary, raise the potential of those incoming pipes to the same (above earth) potential as the MET.

Kind Regards, John