installing main earth bonding conductors to gas and water services

[HawkEye244]

Hi all,
I want to earth the gas and water pipes to the CU and I'm looking at cable sizing. It would be good to do the work to regs and according to my literature it's 16mm2 but it seems that the 16mm2 can be brought down to 10mm2 in an earthing terminal block. Can I run the gas in 16mm2 into a terminal block below the floor joists and then 10mm2 thereafter into the CU? Or does everything need to be in 16mm2?
Is equipotential bonding now no longer a requirement ?
In the case of earthing the gas pipework, can the pipework on the opposite side of the brick wall that the meter is fitted to be sufficient? My literature says it needs to be within 600mm and as near as possible to where the pipes enter the building.
How is the cable fitted to an outside brick wall and how far apart do the clips need to be?
Does it matter if the cable is exposed to the weather?
Help appreciated.

 

[EFLImpudence]

I want to earth the gas and water pipes to the CU and I'm looking at cable sizing. It would be good to do the work to regs and according to my literature it's 16mm2 but it seems that the 16mm2 can be brought down to 10mm2 in an earthing terminal block. Can I run the gas in 16mm2 into a terminal block below the floor joists and then 10mm2 thereafter into the CU? Or does everything need to be in 16mm2?
Is equipotential bonding now no longer a requirement ?

Yes, Main Bonding is required for extraneous-conductive-parts. If not conductive-parts then not possible.
Bonding conductors have to be 10mm². Bigger doesn't hurt but no point.

In the case of earthing the gas pipework,

No, it's bonding; not earthing; needed because it is already earthed by the ground. That's why it needs bonding - joining electrically.
If it is not earthed by the ground, because it is plastic (unlikely for gas), then bonding is not required.

can the pipework on the opposite side of the brick wall that the meter is fitted to be sufficient? My literature says it needs to be within 600mm and as near as possible to where the pipes enter the building.

It should be "at the point of entry - where practicable". Obviously the point of entry can be outside as well as inside. Ignore the 600mm. - that is wrong.

How is the cable fitted to an outside brick wall and how far apart do the clips need to be?

Any method that works is satisfactory. It depends how neat you want it to look.

Does it matter if the cable is exposed to the weather?

There are external clamps - which might as well be used everywhere.

 

[EFLImpudence]

If you live out in the wilds and have TT earthing - an earth rod - then smaller bonding conductor might be used.


Don't you have any Main Bonding now?

 

[AndyPRK]

16mm is big stuff !
So if you can get away with smaller it’s worth it.
There shouldn’t be any joints in it

 

[EFLImpudence]

There shouldn’t be any joints in it

That is not true.

 

[Taylortwocities]

according to my literature it's 16mm2 but it seems that the 16mm2 can be brought down to 10mm2 in an earthing terminal block. Can I run the gas in 16mm2 into a terminal block below the floor joists and then 10mm2 thereafter into the CU? Or does everything need to be in 16mm2?

What literature are you looking at???

As above I think you have misunderstood.
The minimum sizes of the conductors allowed largely depends on your supply type. The following is for TNC-S with 25 or 16mm² meter tails and is the largest needed for a general domestic supply:

MAIN EARTH - 16mm²
This is the earth from the supply to the main earthing terminal (MET) The MET may be the earthing bar inside the CU, or it may be external to the CU.

Main equipotential bonding conductors - 10mm²
These conductors connect together the installation earthing system (MET) and the metalwork of other services such as gas and water.

If a joint is needed (you shouldn’t need one!) like every other, it must be accessible if it uses screwed terminals.

There’s a reasonable explanation, and some pictures, here. https://electricalapprentice.co.uk/an-introduction-to-earthing-and-bonding/
Worth a read, to get a better understanding.

 

[ericmark]

If you connect an TN-C-S earth to a gas pipe before the isolation block, and the TN-C-S earth is lost, then it can rupture the gas pipe with explosive results, one does need to be careful that a gas pipe can't become the earth for the whole street.

 

[bernardgreen]

one does need to be careful that a gas pipe can't become the earth for the whole street.

and be careful that a metallic water main does not become the Neutral for the whole street and the bonding conductor melts. Could this be the reason that 10mm² is required.

 

[johnny2007]

Not an electrician, but in building kitchens I was always asked by sparks to run a 10mm2 earth cable from metal water pipes to consumer unit in a continuous run, no joints and no matter what distance it was.
They didn't mind it having it clipped to the wall behind cabinets rather than buried.

 

[Taylortwocities]

Not an electrician, but in building kitchens I was always asked by sparks to run a 10mm2 earth cable from metal water pipes to consumer unit in a continuous run, no joints and no matter what distance it was.
They didn't mind it having it clipped to the wall behind cabinets rather than buried.

There’s an organisation who thinks that they make the regulations. They call themselves the NICEIC.
They have a requirement that main bonding conductors must be continuous, but this is not a Regulation in BS7671.

 

[securespark]

I learnt at college in the 80s that if you are running from one pipe to another (eg gas to water) then best practice is to make an unbroken loop around the screw so that if the connection loosens, you don't lose the connection to the pipe at the end of the cable.

 

[Risteard]

What literature are you looking at???

As above I think you have misunderstood.
The minimum sizes of the conductors allowed largely depends on your supply type. The following is for TNC-S with 25 or 16mm² meter tails and is the largest needed for a general domestic supply:

MAIN EARTH - 16mm²
This is the earth from the supply to the main earthing terminal (MET) The MET may be the earthing bar inside the CU, or it may be external to the CU.

Main equipotential bonding conductors - 10mm²
These conductors connect together the installation earthing system (MET) and the metalwork of other services such as gas and water.

If a joint is needed (you shouldn’t need one!) like every other, it must be accessible if it uses screwed terminals.

There’s a reasonable explanation, and some pictures, here. https://electricalapprentice.co.uk/an-introduction-to-earthing-and-bonding/
Worth a read, to get a better understanding.

There is no such thing as a "main Earth". It is called the Earthing conductor.

 

[Risteard]

There’s an organisation who thinks that they make the regulations. They call themselves the NICEIC.
They have a requirement that main bonding conductors must be continuous, but this is not a Regulation in BS7671.

The NICEIC only require adherence to BS7671.

 

[ericmark]

I remember using C crimps to crimp 6 mm to 16 mm on tray work in a petrochemical works. But that is one of the few times in the main even the link wires where only required when the tray was clipped if bolted together not required.

But with copped pipe filled with water the current required to melt the pipe would be massive, but the current to damage the gas flexible pipes is a lot less, I would not worry with TT, but with TN it is hard unless labeled to know if TN-C-S or TN-S.

 

[securespark]

They do make up loads of carp.

An NIC spark had kicked off on a job I was on because a feed to a boiler had been piggy-backed off a 16A circuit feeding one socket.

When I suggested it was fine and showed him the OSG, he snorted,
"WE don't follow that piece of rubbish. Only the regs."

He was adamant it was non-compliant.