Gas Pipe Bonding

[thomp1983]

Hi all,

There's no bonding on our gas pipe as it was replaced not too long ago.

My question today is regards where I have to join onto it.

That's the gas meter outside my house,

That's where the gas pipe runs vertically up into the soffits.

I don't really want the bonding on show next to the front door, can I connect it at the top of that gas pipe in the soffit, that would be approx. 2 metres from where the pipe leaves the gas meter.

My second choice would be to come out of the left side of the meter box and into the porch then up the wall into the loft, this would leave about 25cm of cable on show clipped low down between the box and porch wall.

The cable run back to the henley at the electric meter will be roughly 12m, will 10mm cable be sufficient for this?

Thanks
Chris

 

[EFLImpudence]

The bonding should be connected "at the point of entry to the premises where practicable" so - just outside or just inside where accessible.

If the supply pipe is now plastic it might not require bonding but it will not matter if you still bond it.

Yes, use 10mm² cable.

 

[ericmark]

The bonding does depend on supply type, with a TN-C-S supply there needs to be an isolation between gas pipes inside the house and gas pipes outside the house.

Although rare with a TN-C-S supply it has been known for the supply PEN as it is called to fail, this is the combined neutral and earth, if this happens current can run to any true earth, so if the gas pipe is bonded to the earth on a TN-C-S supply and there is no isolation point on the gas supply it can try to earth through the gas pipe and melt the gas pipe with explosive results.

Pipe work outside if connected to the TN-C-S earth could give one a nasty shock if touched, only pipe work inside should be bonded, personally I would be getting some one who is authorised to work on gas to say where and if it should be bonded.

 

[thomp1983]

So point of entry to the property in this case can be assumed to be where it enters the soffit as it then dog legs left and across into the porch, on which case I can bond it inside the soffit as I wanted to?

 

[EFLImpudence]

Yes.

 

[JohnW2]

... with a TN-C-S supply there needs to be an isolation between gas pipes inside the house and gas pipes outside the house. ...

Where does that come from (other than, perhaps, some people's view of a sort-of 'common sense')??

Kind Regards, John

 

[john4703]

So point of entry to the property in this case can be assumed to be where it enters the soffit as it then dog legs left and across into the porch, on which case I can bond it inside the soffit as I wanted to?

That is interesting as when I had a smart gas meter fitted the installer said that I need to bond the pipe near the meter. the meter is in an external box at ground level, and I live in a first floor flat. The gas pipe is bonded to earth near the boiler, there is about 150mm of gas pipe inside my home, so the bonding is close to where it enters the property. I’m starting to suspect the Smart meter installer was not very smart.

 

[EFLImpudence]

I’m starting to suspect the Smart meter installer was not very smart.

Probably not - on electrical matters.

You should have asked him why and what is the purpose of the bonding.

 

[CBW]

http://www.niceic.com/medialib/www.niceic.com/PDF/Gas-Pocket-Guide-8.pdf

 

[JohnW2]

That is interesting as when I had a smart gas meter fitted the installer said that I need to bond the pipe near the meter. the meter is in an external box at ground level, and I live in a first floor flat.

This whole business does get more complicated when there are multiple dwellings, hence electrical installations, within a single building. However, in terms of 'electrical common sense', it is fairly clear that any metal pipe which enters a building after having been underground should be bonded close to where it enters the building, regardless of where (and how many) electrical installations may be within the building.

Of course, if (as increasingly common) all of the underground pipework is plastic, then there is no electrical reason for bonding anything, even though the pipes entering the building is inevitably metal. I think that is an issue which much of the 'gas community', and some of the 'electrical community' do not seem to understand.

More generally, the main problem with the regulations is..

... The main protective bonding connection to any extraneous-conductive-part such as gas, water or other metallic pipework or service shall be made as near as practicable to the point of entry of that part into the premises. Where there is a meter, isolation point or union, the connection shall be made to the consumer’s hard metal pipework and before any branch pipework.

In most circumstances, the second of those sentences makes no electrical sense, and in some circumstances complying with it could, at least theoretically, create an unnecessary electrical hazard.

Kind Regards, John

 

[EFLImpudence]

Oh, it's unfair to only quote part of the regulation.

544.1.2
"The main protective bonding connection to any extraneous-conductive-part such as gas, water or
other metallic pipework or service shall be made as near as practicable to the point of entry of that part into the premises.
Where there is a meter, isolation point or union, the connection shall be made to the consumer’s hard metal pipework and before any branch pipework. Where practicable the connection shall be made within 600 mm of the meter outlet union or at the point of entry to the building if the meter is external."

I know you have said it can be read different ways but I disagree so as you know the correct way to bond then that must be the way to read it.

 

[thomp1983]

So given I had a new gas service installed last July and I know it's plastic does that mean I don't need the bonding at all?

Does the same apply to my water supply too as I know that's in 32mm mdpe as I fitted it.

Thanks
Chris

 

[EFLImpudence]

So given I had a new gas service installed last July and I know it's plastic does that mean I don't need the bonding at all?

Correct.

Does the same apply to my water supply too as I know that's in 32mm mdpe as I fitted it.

The same applies.

 

[JohnW2]

Oh, it's unfair to only quote part of the regulation. ...

I only quoted the part relevant to the point I was making - namely that to bond on the consumer's side of anything 'insulating' is not only electrically unnecessary but could theoretically actually create an electrical hazard (by unnecessarily earthing metalwork within the building).

In practice, these days, that 'theoretical hazard' will hardly ever be realised, since gas pipework will nearly always already be earthed, via boilers, CH components or cookers etc. which have electrical connections - so bonding it will 'do no harm'. However, in my late mother's house (and undoubtedly still some others), her gas pipework only supplied a couple of 'gas fires', a gas cooker (and, at one point, even a 'gas fridge'), none of which had any electrical connections at all. In that situation, if the meter and/or some 'insulation section' was electrically isolating her internal gas pipework from the incoming gap pipe, that pipework would be truly 'floating' such that earthing it would have introduced a theoretical electrical hazard.

I know you have said it can be read different ways but I disagree so as you know the correct way to bond then that must be the way to read it.

I'm not sure I understand how you can disagree that some people read it differently, since we have seen evidence that some do. Yes, I know how the bonding (when necessary) should be done, and hence what the regs should unambiguously say, but that doesn't alter the fact that some people appear to "read it differently", does it?

Kind Regards, John.

 

[EFLImpudence]

I don't disagree that one part of the regulation, as you say, is wrong.

However, I thought you have previously said that you thought it could be read so that 'that wrong part' also applied to external meters. I disagree that that is the case.