Earth bonding via sub-main??

[BillyTheSparks]

Hi De Hi,

I'm pricing for a small kitchen extension.
The owner of the property has run a 10mm^ 3core SWA around the outside of the building from the garage to supply a new C/U in the kitchen.

All well so far.

The problem is that the Main Water and Gas has not been bonded to the MET!
The water stop cock has been tiled in to some boxing in the shower room, and is unaccessable!! And both are situated the wrong side of the house to the C/U.


It will a pain to have to get the original C/U going under the floors as they have fitted wardrobes/furniture and the joists run the wrong way (typical!!)

As said the SWA is 10mm^ 3core.
Would it be possible to bond the Gas and Water from the new C/U; in the new part of the kitchen?? Using the earth of the SWA (I was going to use the 3rd core as an earth for the new circuits.

Any help would be greatly appreciated

 

[Deleted member 26818]

Yes, you would effectively be using the earth bar in the kitchen CU as an Earth Mashalling Terminal.

 

[tonys]

Spinlondon

Yes, but the main earthing requirements at the origin of the installation will more than likely have be upgraded to a 16mm conductor once an alteration as taken place if its not already that size.

So by using the 10mm core of the swa as a equipotential bonding conductor it would have to be continuous to the Gas & Water pipes without any breaks. So imo it is not suitable.

 

[Deleted member 26818]

Continuous?
There is no requirement in BS7671 for a bonding conductor to be continuous that I am aware of.

 

[tonys]

Continuous?
There is no requirement in BS7671 for a bonding conductor to be continuous that I am aware of.

What, so you would use a 10mm earth then run 10mm bonds from it, when the main earth should be a 16mm ?

 

[BillyTheSparks]

Thank you for your replies,
I have understand that for bonding the gas and water you can use a single conductor, as long as it is continuous. so how about I use the SWA as the Earth for the new C/U and sub-circuits and then use a 10mm to the water and gas (continuous), then Crimp joint the 10mm g/y to the 3rd core of the SWA??

Do you think this would be a way around the problem?

 

[tonys]

"crimp" I was waiting for that one lol

The armour on the swa is equivalent to 4mm copper going by the chart in front of me. Its up to you mate, I know what I would do and keep it to myself.

Is it a pme system ?

 

[Deleted member 26818]

What, so you would use a 10mm earth then run 10mm bonds from it, when the main earth should be a 16mm ?

I don't understand.
Where have I suggested that 10mm² main earth should be used?
I have no idea what size the main earth is, as the OP has not made that information available.
What does the size of the main earth conductor have to do with your suggestion that bonding conductors have to be continuous?

 

[tonys]

I don't understand.
Where have I suggested that 10mm² main earth should be used?
I have no idea what size the main earth is, as the OP has not made that information available.
What does the size of the main earth conductor have to do with your suggestion that bonding conductors have to be continuous?

Where did I say 10mm main earth?

 

[Deleted member 26818]

In post No.5. The one I quoted.

 

[SimpleSimon]

I think you gents have got your wires crossed (pardon the pun).

 

[BillyTheSparks]

"crimp" I was waiting for that one lol

The armour on the swa is equivalent to 4mm copper going by the chart in front of me. Its up to you mate, I know what I would do and keep it to myself.

Is it a pme system ?

Ah! Well that blows that out of the water then!
I have got that table regarding the CSA of SWA cable amouring, but can't find it at the moment.

Sorry to be prdictable about the crimp joint

I'm going to go back tomorrow and have another look and hopefully take note of everything properly. I cant recall the supply details.

If I need to have carpet and floor boards up, I will. He'll just have to lump it.

I just wanted a simple job.

Thanks for your time and extended knowledge

 

[Deleted member 26818]

The minimum CSA for a bonding conductor where PME conditions apply where the neutral conductor is 35mm² or less is 10mm².
The copper equivilance only applies to the bonding conductor. There is also no reason why conductors cannot provide more than one function.
As such ther is nothing wrong in using the 10mm² core as a bonding conductor bonding between the CU earth bars, and the armour as a CPC for the distribution circuit.
I have no idea what Tonys is going on about, or why he is spouting nonsence.

 

[Engineer54]

Seems to me, it's another case of using multiple CUs in a single dwelling unit. And again from the plan given by the OP, a totally unnecessary one!!!

Who laid that SWA cable?? what sort of bending radius's have been used in it's installation?? Was there any sheath damage to the cable during it's installation?? Are you going to do a sheath test before connecting this new kitchen supply to the mains??

Who in there right mind would permanently box off the main water stop cock to the building??

 

[Deleted member 9648]

Seems to me, it's another case of using multiple CUs in a single dwelling unit. And again from the plan given by the OP, a totally unnecessary one!!! ....The Horror...

Who laid that SWA cable?? what sort of bending radius's have been used in it's installation?? Was there any sheath damage to the cable during it's installation?? Are you going to do a sheath test before connecting this new kitchen supply to the mains??WTF is a sheath test?...edit...that may have been answered by johnboy below...presumably an IR test from the armouring to a ground electrode with the armouring isolated from any earthing??

Who in there right mind would permanently box off the main water stop cock to the building?? builders have never been right in the mind

.........