Water & Gas 16mm/sq

[Ross1]

Hi,

I have to bond the water and gas on a TT installation, the electrode has a 10mm/sq to it already. Its my mate`s house and I`m adding a new lighting circuit for my DI assessment. My mate has got some 16mm/sq G & Y lying around. Can I use this to bond the gas & water while the main protective conductor remains at 10mm/sq?

Thanks

 

[Deleted member 26818]

Yes you can.

 

[Johnny-G]

I *believe* I'm right in saying that the conductors on a TT system only have to be 4mm max if they're not buried so you can do what you like above that.

 

[telectrix]

with the price of 16mm, i'd save it for main earthing on other jobs and buy some 6mm for this one.

 

[Deleted member 26818]

Minimum CSA for earthing conductors, is 2.5mm² (if sheathed).
Minimum CSA for bonding conductors, is 6mm².

 

[johnboy6083]

the CSA of the earthing conductor in TT installations is governed by the Ra of the rod. the lower the resistance, the higher the fault current, and the larger the cable needs to be as a result.

 

[Johnny-G]

I'll hold my hands up to knowing little about TT requirements (through necessity) and even after having a look through the OSG I can't find 6mm mentioned. Could you point me in the right direction please?

Minimum CSA for earthing conductors, is 2.5mm² (if sheathed).
Minimum CSA for bonding conductors, is 6mm².

 

[Ross1]

I did a Ze test a while back on this one and got a reading of about 150 ohms which to me is ok ( under the 200 ohm mark ). It was the 16mm gas and water I was wondering about.
How does that sound mate?

 

[Deleted member 26818]

I'll hold my hands up to knowing little about TT requirements (through necessity) and even after having a look through the OSG I can't find 6mm mentioned. Could you point me in the right direction please?

"544.1.1 Except where PME conditions apply, a main protective bonding conductor shall have a cross-sectional area not less than half the cross-sectional area required for the earthing conductor of the installation and not less than 6mm²."
The 2.5mm² is mentioned in Table 54.1 and Regulation 543.1.1.

 

[Glen Stimson]

I did a Ze test a while back on this one and got a reading of about 150 ohms which to me is ok ( under the 200 ohm mark ). It was the 16mm gas and water I was wondering about.
How does that sound mate?

personally 150 ohms would be the limit, yes its fine but anything higher i would defo consider extending or adding another spike.