CU Change and Main Protective Bonding

[SJD]

I can't be bothered to read it all again so I'm sorry if I have forgotten or missed a bit.

Except for TNC-S the adiabatic is used to determine the csa of the earthing conductor.
This may work out to, say, 12mm but that means, of course, you would need to fit 16mm.

However, this would also mean that the bonding can be 6mm - half of 12, not half of 16.

It is not a straight question of what should I fit.

The question specifically relates to TN-C-S, and the situation when it is difficult to follow the regs.

 

[Geoffsd]

Does it not, then, come down to the regs. not being retrospective?

 

[rattlehead85]

The way forward with this should be.
1. Check the continuity and condition of the existing 6mm2 bonding. If there are no signs of corrosion or overheating at the connections and they are adequately labeled and soundly made you can proceed with the fuse board replacement.
2. Fit your fuse board ensuring you provide correct protection and board configuration.
3. Complete your EIC stating the following in the extent of works box. "Replacement of existing consumer unit with condition check and continuity verification of existing 6mm2 bonding for continued service"

With this you have explained what work you have completed and what steps you have taken to ensure the installation was of no safety concern on the day you completed the work. The regulations are NOT retrospective. On an EICR 6mm2 bonding on a TN-C-S system warrants a code C3 departure which does NOT suggest an unsafe condition. However if the sizing of the bonding is less than 6mm2 or evidence of deterioration is present this would require attention as a C2 departure would be justified as an unsafe condition.