Main protective bonding

[waynelester]

Hi,can anyone give me some advice,i have installed a sub consumer unit which is fed from main cu using 6mm t&e.i have realised that the earth bonding should be 4 mm and not the 2.5mm.from the main board(earth terminal block) is a main protective bonding to the water main (10mm) which passes right past my sub board.my question is can i divert to my sub cu and then to the water main or is this a no no

 

[WayneL]

Hi,can anyone give me some advice,i have installed a sub consumer unit which is fed from main cu using 6mm t&e.i have realised that the earth bonding should be 4 mm and not the 2.5mm.from the main board(earth terminal block) is a main protective bonding to the water main (10mm) which passes right past my sub board.my question is can i divert to my sub cu and then to the water main or is this a no no

Yes you could, but I don't see why you would want to.

The 2.5mm isn't 'earth bonding', as you call it.

It's a CPC for your CU sub-main circuit -

the only time it would need to be 10mm is if you were using it as both a CPC and Protective Bonding conductor (i.e. using the earth terminal in your sub CU for bonding to)

Where is the sub CU located?

 

[waynelester]

Thanks for that,the sub cu is situated at the end of the house approx 7m and will supply a new kitchen and shower room.the existing is on the only ring in the house so i wanted to have a seperate ciruits so i will run a single 6mm t&e t to the new cu and then supply new circuits to that.i was under impression that the 6mm was distribution circuit and earth should be no less than half the line conductors ie 4mmm