Additional earth electrode

[dingodeano]

Looked at a job i am currently pricing for.
Existing supply at front of house is TT . the earth electrode resistance is well within limits. Customer is having an extention at rear or property. new circuits cannot be fed from existing board because of exposed beams (its a feature) and other cable routing 'issues'. so i proposed a second c/u in new extension fed from a swa cable ran round exterior of property. my question is this should i put in another earth electrode at rear of property? or just simply export earth along with live conductors? .

 

[comms]

The existing rod will suffice.

 

[Spark123]

Existing rod is a must - you want all ECPs in the same equipotential zone to be linked to the same MET.

 

[dingodeano]

Existing rod is a must - you want all ECPs in the same equipotential zone to be linked to the same MET.

ECP? Do you mean cpc. Yes i am not going to touch the existing rod (although i will probably add a nice inspection pit which is not there at the moment).i was just wondering if an additional electrode with proposed consumer unit would be beneficial.

 

[Spark123]

ECP = exposed conductive parts or extraneous conductive parts - I mean both.
How I read your original proposal was to have two separate earth rods to the two separate consumer units both feeding apparatus within the same equipotential zone.

 

[comms]

But the earth potential will be the same at either cu after all both rods would be in terra firma

but like spark123 said I'd stick with the one rod for both cu's.

 

[Spark123]

They may both be in contact with terra firma, however if there is a fault on one system connected to one rod, another system connected to a sepatate rod may be at another potential resulting in a PD between simultaneously accessable ECPs.
If they are both connected to the same MET and this used for the reference for all ECPs then it isn't a problem.

 

[Pensdown]

Have you considered getting the supply converted to TNC-S as part of your works. It makes things so much easier.