Gas bonding

[SUNRAY]

I was in discussions today about gas supplies. This is a 3 story block of flats (oops sorry - apartments). The gas meters are in groups of 3 in wedge shaped meter boxes at ground level and dotted around the building, the pipes run from the meters vertically up the outside of the building and enclosed in semi-circular capping big enough to accommodate the 3 pipes and their 10mm bonds.

My question is - should the 3 services be bonded together or left separate? The U/G feed is plastic.

 

[EFLImpudence]

They only need to be bonded at the point of entry to each flat to each flat's earthing terminal IF they are extraneous-conductive-parts; that is, IF the pipes are electrically connected to metal pipes which emerge from the ground.
The plastic supply would seem to indicate they are not. If not then no bonding is necessary.

In either case, they should not be connected together outside.

 

[SUNRAY]

Now this is really interesting,

They only need to be bonded at the point of entry to each flat .

That was my interpretation but the other 3 reckoned the connexion had to be near the meter .

to each flat's earthing terminal IF they are extraneous-conductive-parts; that is, IF the pipes are electrically connected to metal pipes which emerge from the ground.
The plastic supply would seem to indicate they are not. If not then no bonding is necessary.

This is a recent property (Circa 5 years) and fully bonded.

In either case, they should not be connected together outside.

Quite by chance we were standing outside chatting and noticed one set has the 3 pipes bonded together and another does not, our view had a 50:50 split as these are physically so close. We further discussed whether these should be bonded to the lightning conductor which runs adjacent to the pipes. Edit: In both I say no.

 

[EFLImpudence]

Now this is really interesting, That was my interpretation but the other 3 reckoned the connexion had to be near the meter .

They are wrong.

This is a recent property (Circa 5 years) and fully bonded.

What do you mean by fully bonded?

Quite by chance we were standing outside chatting and noticed one set has the 3 pipes bonded together and another does not, our view had a 50:50 split as these are physically so close.

Did anyone offer a view as to why anyone would want their gas pipes connected to next door's electrical supply?

We further discussed whether these should be bonded to the lightning conductor which runs adjacent to the pipes. Edit: In both I say no.

Correct.
Bonding is to equalise potential (voltage) between touchable parts - lightning???.

 

[SUNRAY]

What do you mean by fully bonded?

25mm² from earth bar to CU then 10mm² to gas, water, building steelwork and one more which goes up into the inaccessible loft space.

Did anyone offer a view as to why anyone would want their gas pipes connected to next door's electrical supply?.

Under fault conditions one could be at a higher potential than the others, the meters are in a public space and the kids tend to sit on them, there is the possibility that one could be in contact with the pipework.

 

[EFLImpudence]

25mm² from earth bar to CU then 10mm² to gas, water, building steelwork and one more which goes up into the inaccessible loft space.

As explained, the gas and water bonding might not be required, but as they are likely connected to appliance CPCs, it probably doesn't matter.
I can't comment on the other two. Is the steelwork accessible in the flats?

Under fault conditions one could be at a higher potential than the others, the meters are in a public space and the kids tend to sit on them, there is the possibility that one could be in contact with the pipework.

I suppose that could be a possibility (until the OPD opens) but you would then be making live all the earthed parts in the neighbours' flats.
Also, all the pipes (rather than just one) will be at a different potential to the ground.
You have to decide which is less likely to cause a hazard.

The meters must surely be in an enclosure (cupboard) so it would be better to insulate the pipes as far as the children can reach.

 

[JohnW2]

Under fault conditions one could be at a higher potential than the others, the meters are in a public space and the kids tend to sit on them, there is the possibility that one could be in contact with the pipework.

That's an interesting point but, regs-wise, I don't think that the scope of BS7671 extends to conductive parts before they enter 'the premises'. Are there perhaps some other relevant regs (ESQCR?) I wonder?

Kind Regards, John

 

[SUNRAY]

As explained, the gas and water bonding might not be required, but as they are likely connected to appliance CPCs, it probably doesn't matter.
I can't comment on the other two. Is the steelwork accessible in the flats?

The staircases are metal, albeit carpeted treads and painted banister, and the external balconette is galvanised.

I suppose that could be a possibility (until the OPD opens) but you would then be making live all the earthed parts in the neighbours' flats
Also, all the pipes (rather than just one) will be at a different potential to the ground.
You have to decide which is less likely to cause a hazard.
The meters must surely be in an enclosure (cupboard) so it would be better to insulate the pipes as far as the children can reach.

They are in the 'standard' brown wedge shaped box which are normally partially buried (not in this installation) the capping stops short of the boxes so there are exposed pipes.

I must add there doesn't seem to be any sort of electrical issue with these buildings, it was just the 4 of us happened to be chatting and seeing them.

I think I know where the 'other' green/yellow goes, the aerial distro has several on the earth rail.

 

[EFLImpudence]

The staircases are metal, albeit carpeted treads and painted banister, and the external balconette is galvanised.

Do you mean the flats' communal stairs?

Unless they are extraneous-conductive-parts in contact with the ground then they should NOT be bonded.

They are in the 'standard' brown wedge shaped box which are normally partially buried (not in this installation) the capping stops short of the boxes so there are exposed pipes.

That would seem to be shoddy, to say the least. Is it supposed to be like that?

I must add there doesn't seem to be any sort of electrical issue with these buildings, it was just the 4 of us happened to be chatting and seeing them.

You may have noticed some hazards caused by poor workmanship.

 

[SUNRAY]

Do you mean the flats' communal stairs?

Unless they are extraneous-conductive-parts in contact with the ground then they should NOT be bonded.
That would seem to be shoddy, to say the least. Is it supposed to be like that?
You may have noticed some hazards caused by poor workmanship.

I've been back on this now and can confirm the gas pipe is bonded after the internal valve where it enters the flat.

Pic shows different meters to the sets I looked at before at another area of the development, it shows pipes are bonded together at the meters (some is inside capping) then they appear to be bonded to ground floor flat

 

[bernardgreen]

Bonding the three gas pipes together at ground level is probably acceptable provided that the electricity supplies to three flats have the same Neutral.

If each gas pipe is bonded to the Main Earth Terminal in it's own flat and the flats do not have the same electrical supply Neutral then any connection between the gas pipes at the meters will be a connection between two different network supply Neutrals.

If the Neutrals are not at the same potential then significant currents will be flowing from one gas pipe to the others through the pipe to pipe bonding cables.

 

[SUNRAY]

Bonding the three gas pipes together at ground level is probably acceptable provided that the electricity supplies to three flats have the same Neutral.

If each gas pipe is bonded to the Main Earth Terminal in it's own flat and the flats do not have the same electrical supply Neutral then any connection between the gas pipes at the meters will be a connection between two different network supply Neutrals.

If the Neutrals are not at the same potential then significant currents will be flowing from one gas pipe to the others through the pipe to pipe bonding cables.

Where do the neutrals come into this?
All the earths are on a common bussbar.

 

[EFLImpudence]

The cable going through the wall could have been the easiest way to correctly bond the flat on the other side.
The cable going under the capping does not seem to be necessary.


The same for this one although it is not clear.

 

[SUNRAY]

View attachment 145646

The cable going through the wall could have been the easiest way to correctly bond the flat on the other side.
The cable going under the capping does not seem to be necessary.


The same for this one although it is not clear.

View attachment 145647

Under the capping are 2 more earth clips, all 3 pipes are bonded together in both of these sets of meters.

The block referred to in OP, at least one set of 3 are not bonded together and one set of 3 is, hence the thread.

EDIT: approximate arrangements

 

[EFLImpudence]

I would think someone has just not understood "bonding" and has thought everything must be "earthed" - or, at least, connected together with green and yellow cables.