Earth bonding on gas inlet pipe

[newvilles]

Hi all,

I waited in for most of the day today to get my gas meter replaced but the engineer who called said he couldn't replace it because we have our bonding on the gas inlet and not outlet... I can't really understand what difference it makes, could someone more knowledgeable then me maybe explain the reason why?

He said that it was his companies policy not to change the meter because as it was on the inlet and not the outlet then there could be a risk of a shock or spark even if he used some kind of temporary connection and our consumer unit also wouldn't trip but would if it was on the outlet.

I hope this make sense & thanks.

 

[SaladFingers]

What an idiot and a load of tosh.

 

[JohnD]

if you have a screwdriver you could undo the clamp and fit it onto the other pipe yoursel.

or if you pay me £50 plus 40p/mile I'll do it for you.

 

[Stevoon]

If the meter fitter was that concerned could he not of turned the mains off whilst he swapped the gas meter? That being said I think some meter fitters seem to find any excuse not to complete the job, I've had one bounce a 3 Phase meter install as he "didn't like the look of the job" and another because he had no change to park as it was close to christmas!

 

[bernardgreen]

The "earth" inside the house may not be at the same potential as ground. ( This is not a hazard for people in the house ).

If the earth bond to the gas pipe is on the house side of the meter then the earth connection to the gas pipe work is not broken when the meter is changed.

If the earth bond is on the inlet to the meter then removing the meter will break the earth bonding of the gas installation. When this break happens any difference in potential may cause a spark that could ignite gas coming from the disconnected gas pipe.

The risk is minimal and the meter man should have been less jobs-worth and more helpful by suggesting the bond be moved while he enjoyed tea and choccy biscuits.

 

[RF Lighting]

It doesn't matter on which side the bond is made, the hazard of sparking and the revelation of PD upon removal of the meter can present it's self in either situation.

This is why it is in the gas regs that you must fit a temporary bond between the two pipes before removing a meter.

Why do you insist on putting earth in quotation marks? It is the earth, despite what ever misconceptions you have about it.

 

[HERTS P&D]

Jobs-worth!!!

Andy

 

[JohnW2]

Why do you insist on putting earth in quotation marks? It is the earth, despite what ever misconceptions you have about it.

I have to say that I have some sympathy with Bernard in the case of TN-C-S, in which case the 'earth' in the house is, in fact, the supply neutral. Sure, that will almost always represent a good path to earth - but it is 'indirect'. The analolgy I would use are road signs - if a turning does not take you directly onto the A999, but provides a path to it, they put the 'A999' in brackets on the sign; I see Bernard's quotation marks as being equivalent to that.

Such a convention at last tidies up language and concepts about main protective bonding. It is required if there is a conductor (an extraneous-conductive part) which is "liable to indtroduce a potential, usually [true] earth potential...". If the 'earth' within an installation really were true earth (without quotation marks) there would never be any point in, or need for, MPB.

Kind Regards, John

 

[JohnW2]

If the earth bond to the gas pipe is on the house side of the meter then the earth connection to the gas pipe work is not broken when the meter is changed. If the earth bond is on the inlet to the meter then removing the meter will break the earth bonding of the gas installation. When this break happens any difference in potential may cause a spark that could ignite gas coming from the disconnected gas pipe.

IMO, that logic is all wrong. Similar risks exist regardless of which side of the meter is bonded and, it can easily be argued that the risk is actually likely to be greater if the bond is on the house side of the meter.

Kind Regards, John

 

[RF Lighting]

If the 'earth' within an installation really were true earth (without quotation marks) there would never be any point in, or need for, MPB.

So by that logic, MPBs are not required on TT supplies then?

 

[JohnW2]

If the 'earth' within an installation really were true earth (without quotation marks) there would never be any point in, or need for, MPB.

So by that logic, MPBs are not required on TT supplies then?

Well, no - and that's the whole point. As you are well aware, under fault conditions, the thing within the installation you would like to call earth (without any qualifying quote marks) can, in a TT installation, rise to close to the Line potential relative to [true] earth (hence the need for MPB). To call that earth, without any qualification, seems a little odd to me.

Kind Regards, John

 

[PrenticeBoyofDerry]

Gas meter man is a ****** simples.
You put a temp bond between supply and consumer side, change meter, remove temp bond, advise client that the MEB is incorrectly installed.
No probs to the ******, job done with very little extra work.

 

[JohnW2]

Gas meter man is a ****** simples. You put a temp bond between supply and consumer side, change metre, remove temp bond, advise client that the MEB is incorrectly installed. No probs to the ******, job done with very little extra work.

I would have said No extra work, apart from advising the client - that temporary bond is essential, regardless of which side of the meter the MPB/MEB is connected to.

Kind Regards, John

 

[Lectrician]

If the meter fitter was that concerned could he not of turned the mains off whilst he swapped the gas meter?

Have a think about earthing, bonding and double pole isolation......and whether the earth is switched...

 

[bernardgreen]

Why do you insist on putting earth in quotation marks? It is the earth, despite what ever misconceptions you have about it.

I do it because other than in a TT system the CPC is not at earth (as in ground) potential.

The CPC in systems that are not TT is connected to a ground rod via a conductor BUT because that conductor is also carrying load currents it will have a voltage drop along it so the CPC cannot be at ground potential.

When PME and other non TT systems came into being the "earth" wire should have been re-named to be the CPC.