Main Protective Bonding

[imroberts]

I have a couple of questions. I searched for an answer however couldn't find anything that answered them.

- If the gas or water supply pipes are, say, at the opposite side of the house to the electric meter and CU, meaning a long main protective bonding conductor is required, does this need to be run in safe zones as with live cables, and does it need to be accessible along it's entire length?

- Is there a limit to the length (or resistance) of the main protective bonding conductor which would require increasing the CSA from the "norm"?

 

[RF Lighting]

If the cable is concealed within a wall or partition then yes it will need to be in a safe zone.

It does not need to be accesible for inspection throughout it's entire length, only at the ends where it is terminated.

The max resistance is 0.05Ω for a main bomding conductor.

 

[imroberts]

Thanks RF

Where is the max resistance of 0.05ohm stupilated?

 

[EFLImpudence]

Where is the max resistance of 0.05ohm stupilated?

I think it's more of a guide line should you come across old main bonding which is smaller than 10mm².

10mm² cable would have to be longer than 27 metres to have a resistance greater than 0.05Ω.

 

[imroberts]

I think it's more of a guide line should you come across old main bonding which is smaller than 10mm².

10mm² cable would have to be longer than 27 metres to have a resistance greater than 0.05Ω.

That would explain why I don't recall reading it in the regs

Thanks muchly!

 

[Taylortwocities]

It is not in BS7671

but

Guidance Note 3, Inspection and Testing, published by the IEE, advises that supplementary equipotential bonding conductors should have a resistance of 0.05Ω, or less.

So, a guide and not a regulation, maybe/?