MAIN EARTH BONDING domestic installation

[piz]

Hello
When we are asked to change a CU i have been told on pme and tns the main earthing conductor is the responsibilty of the electricity board.
so if this is the case why is a 16 mm earth sold on packs of 2meter tails?,
example change board 25mm tails or 16mm if 80amp main fuse 10mm to gas and water but only sometimes 4 or 6 mm main earth do we just record this on an EIC
Cheers

 

[Engineer54]

542.3.1:
Protected against corrosion and mechanical = 2.5mm copper
Protected against corrosion and not mechanical = 16mm copper
Not Protected against corrosion and not mechanical = 25mm copper

Most properties in Pembrokeshire with TT are not protected against corrosion or mechanical protection so must be 25mm

To terminate 25mm into a CU is a pain I had to split the cable to 4/3 wires and terminate that way over 2 connections - NAPIT said that was the best way

The PVC sheath is the protection against corrosion. Bare copper conductor is the type of cable not protected against corrosion... I wouldn't use 16mm for a domestic UK TT system with an Ra value hovering around 200 Ohms!! lol!!

 

[Engineer54]

Either way in Pembrokeshire its not possible because all the rods have been concreted to make a path - i will take the trunking idea into consideration next time

Shame they didn't install a concrete earth rod pit on the rod and buried the earth conductor in the path too!! Why not run this cable in a metal of heavy duty PVC conduit between rod and where it enters the house, even better chasing the cable into the path. Surely got to be better than a a cable running across a pathway??

 

[spark 68]

Nicholas I have used a Max csa of 16mm before where there is no alternative (or at least a cheap alternative) but never 25mm on a domestic TT, as I say I usually just use 10mm simply because I carry this size for main bonding purposes anyway.