earth to second consumer unit

[prince of darkness]

hello dudes happy christmas!

If a feed a second consumer unit from the main one with some 10mm T&E on a 45A mcb will I need to run a 16mm main earth across to it or will the cpc in the T&E be sufficient?

 

[ban-all-sheds]

I'd make it at least 10mm²..

 

[Lectrician]

Table 54g - Use 6mm.

You would not be able to connect any main equipotential bonds to that second CU though, unless you upped the earth size.

 

[Adam_151]

10mm² would be the easy way to make sure its sufficent, table 54G would then be satisfied, if we didn't want to do this, and wanted to know if the 4mm² was sufficent, we could calculate the adiabatic if we really wanted to!

Regardless of thermal withstand calculations, you need to make sure the EFLI figures are in spec for both the submain circuit and for those circuits fed from it

Are you planning on notfiying this work to your local building control office?