Earth for gas meter question

[shd1970]

Hi all,

I have had my gas meter moved from inside my house, to a semi concealed (the small, floor level brown box type) outside and at the front of my house.
The gas pipe that feeds my gas appliances comes stright through the wall into my kitchen, right under the kitchen sink.

My gas fitter has said that i need to fit an earth bond ".....within 500mm" of the gas meter.

So questions :

1 - Is this correct ?
2 - If so, presumably i can just attach an earth strap to the 22mm copper as soon as it comes through the kitchen wall ?
3 - Can i run this new earth just to where my main water feed comes in and clip onto that strap as its earth cable is brand new right back to the RCD ?

Thanks in advance all.

Sean

 

[PrenticeBoyofDerry]

1 - Is this correct ?

No, ideally within 600mm of entering the property or it can be terminated inside the meter cabinet but terminated after the meter or if non of these can be achieved then where practical but this must be documented on any certificates.

2 - If so, presumably i can just attach an earth strap to the 22mm copper as soon as it comes through the kitchen wall ?

As above

3 - Can i run this new earth just to where my main water feed comes in and clip onto that strap as its earth cable is brand new right back to the RCD ?

You can cross connect both gas and water mains using just the one bonding conductor, ideally these should be a continuous length(unbroken), but others will disagree. An unbroken length would would maintain the connection to the gas pipe, should the the water pipe bond become loose or disconnected.
Depending on the type of earthing arrangement you have, the CSA of the bonding conductor would be expected to be 10mm2 CSA and give you a reading of less than 0.05Ω between termination ends (form CU/MET to bond of pipe)

 

[ericmark]

544.1.2 The main equipotential 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 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.

That's what the book says.
In real terms with soldered pipes I am sure the pipe is a better conductor than an earth cable so I would not worry as to where it was bonded. The idea is all metal work in the house should be at the same voltage. So if there was a fault even if for example the neutral/earth of the TN-C-S supply was lost (very unlikely) you could not touch two bits of exposed metalwork having a different voltage.

As to you having to fit the earth I question that? I would have said the gas fitter should not have left the premises without re-instating the earth.

I will always test an earth. Although one would hope nothing could go wrong fitting a simple earth wire I have seen errors where something has insulated the connection as simple as a wire pushed in too far so gripping insulation not copper. So I would not have thought it should be left to householder to do the work that I would have thought was his job?

 

[shd1970]

thanks for the replies guys - appreciated.

So within 600mm which is perfect....the new copper on my side of the meter comes into the house only 300mm away from the meter so thats fine.
The work was only completed late on Friday due to issues moving the meter and obviously there was no previous earth as this was a new move which was why i would said that i would sort the earth for the gas guy.

Eric - do you have any thoughts on that prentice said which can be a bone of debate, ie, can i run just a short earth lead onto the bonding that is already installed onto my cold water pipe ?
This earth is a brand new earth run only 3 months ago and straight back to the RCD.

Also, can you confirm what thickness of earth cable is required for this type of bonding please ?

thanks again guys for your help......

 

[PrenticeBoyofDerry]

Eric - do you have any thoughts on that prentice said which can be a bone of debate, ie, can i run just a short earth lead onto the bonding that is already installed onto my cold water pipe ?

This is guideline as stated in guidance note 8 2001 amd No1 2002 and No2 2004 and is not a requirement but if you could run an unbroken length between CU-water-gas, this would avoid problems if water bond became disconnected. But in your case for practical reasons there is nothing preventing you from making a link bond between both gas and water. Better in place than not.

This earth is a brand new earth run only 3 months ago and straight back to the RCD.

I assume you mean the consumer unit met busbar?

Also, can you confirm what thickness of earth cable is required for this type of bonding please ?

It is standard practise to install 10mm main bonding and 16mm earthing conductor on TT, TNS and TNCS systems.
This is belt and braces, you can do a calculation that will give you your minimum requirements.

 

[shd1970]

thanks again Prentice........off to screwfix now for my bits and bobs, and yes i meant back to the main buzz bar

thanks for your input....really appreciated.

 

[riveralt]

thanks again Prentice........off to screwfix now for my bits and bobs, and yes i meant back to the main buzz bar

I trust you meant the main earthing terminal.

 

[shd1970]

Hi again guys,

Just a further piece of info that i forgot to mention earlier, but as i had my meter moved and they had issues with my main supply (leak in the steel pipe in the road), they actually laid us a brand new plastic feed supply from the road.

The electrician in B & Q that i spoke to who is currently reading up on the current regs to sit his exam in the next 2 weeks showed me that in section 4.5 of his onsite ring-binder guide (17th edition) that if the supply is plastic, then no bonding is required.

Are you guys aware of this and sorry if this crucial piece of info wasted anyones time

 

[PrenticeBoyofDerry]

If the pipe work within the house is metallic, should still be bonded after the insulated pipe. I think eric touched on this in his post!
If the pipes within the house are plastic then bonding can be omitted.

 

[GaryMo]

If it's plastic and contains gas then it can't introduce a potential within the equipotential zone (your four walls) from outside. In that case it's not extraneous (verified by having a resistance of more than 23Kohms between the pipe and MET) so no bonding required.p

 

[EFLImpudence]

I don't have a green OSG (new one) - I assume it's the same.

Section 4.5 refers to supplementary bonding - not what this is.

4.4 refers to main bonding and states while it may not be needed (now in your case) it is still recommended.

 

[PrenticeBoyofDerry]

read requirement 544.1.2

 

[PrenticeBoyofDerry]

The electrician in B & Q that i spoke to who is currently reading up on the current regs to sit his exam in the next 2 weeks showed me that in section 4.5 of his onsite ring-binder guide (17th edition) that if the supply is plastic, then no bonding is required.

Tell the electrician in B&Q that he needs the big green book not the red OSG. If they wants to be successful in the exam.

 

[PrenticeBoyofDerry]

I don't have a green OSG (new one) - I assume it's the same.

Section 4.5 refers to supplementary bonding - not what this is.

4.4 refers to main bonding and states while it may not be needed (now in your case) it is still recommended.

4.5 in green OSG refers to water and space heaters.

 

[GaryMo]

read requirement 544.1.2

'An insulating section' - the whole lot entering is insulated and cannot introduce a potential thus is not extraneous.

411.3.1.2

In each installation main protective bonding conductors complying with Chapter 54 shall connect to the main earthing terminal extraneous-conductive-parts including the following:
(i) Water installation pipes
(ii) Gas installation pipes
(iii) Other installation pipework and ducting
(iv) Central heating and air conditioning systems
(v) Exposed metallic structural parts of the building.

Extraneous-conductive-parts are mentioned which includes gas installation pipes. If they're not deemed to be extraneous-conductive-parts then how can they be relevant?