Replacing Main Earthing Conductor

[Clink]

This may be a newbies question but the older and wiser (or at least the more experienced) heads out there may be able to help....

Just inspected a clients house and amongst the, many, problems it only has a 6mm Main Earthing Conductor. I intend to upgrade it to 16mm but I can't see how to access the earth connector in the supplier's service head. Do I really need to contact the DNO to upgrade an earth? This seems excessive and possibly expensive.

 

[Engineer54]

They used to use (and perhaps still do in some cases) a split concentric cable, where one half of the outer sheath was the neutral and the other half the earth.
These cables were often made off in the head, and unless the link between the neutral and earth was made, they were TN-S, but without removing the cover, there was no way to tell.

Yep, i can see now what your saying!! Completely forgot about the split concentric type of cable... lol!!

 

[Clink]

Thanks guys, sorry for the slow response to questions, but yes it is TN-C-S and yes the Ze is in limits. My initial reaction was to replace it but having looked a bit further into the figures and there are no signs of deterioration I'm going to leave well alone.

 

[T&Earth]

Hi Dagrat

As above, do the adiabatic. you will probably find that 6mm is adequate. If so leave it in

When doing the adiadatic for say earthing & main bonding conductors where do you take the PEFC from? On a final circuit you would take it between Mcb Line & Earth.

Any advice would be appricaited

Many Thanks

 

[Richard Burns]

Hi Dagrat


When doing the adiabatic for say earthing & main bonding conductors where do you take the PEFC from? On a final circuit you would take it between Mcb Line & Earth.

Any advice would be appreciated

Many Thanks

The adiabatic equation does not apply to main bonding conductors, they are sized from the size of the incoming neutral for PME supplies or by the size required for the earthing conductor on non PME supplies.

For any installation the highest prospective fault current is found at the supply source. So PEFC is measured between the incoming line to the MET.
Anywhere else in the installation the fault current will drop because of the resistance of the wiring so work with the worst case (at the source).

 

[Deleted member 26818]

Hi Dagrat


When doing the adiadatic for say earthing & main bonding conductors where do you take the PEFC from? On a final circuit you would take it between Mcb Line & Earth.

Any advice would be appricaited

Many Thanks

The PEFC would be determined when measuring Ze/Zs at the origin of the installation.