protective equipotential bonding cable size?

[ericmark]

To quote from Electrical Safety Councils web site
“EDQ12 When carrying out electrical work on an installation forming part of a TN-C-S system, is it necessary to upgrade existing 6 mm² protective equipotential bonding to 10 mm²?
EDA12 Not necessarily. If the existing 6 mm² bonding connects all the extraneous-conductive-parts to the main earthing terminal, has been in place for a significant time and shows no signs of thermal damage, then it may not require to be upgraded. Regulation number 701.415.2”.
May be my old age but is not section 701 only to do with bathrooms? Note there is no “supplementary” in wording. I would have been looking at Tables 54.7 which says 16 mm² not 10 mm² and defiantly not 6 mm² for let us remember a TN-C-S supply. I will conceded that with a TT supply or as regulations state not PME then 6 mm² is OK as with regulation 544.1.1 but I was under the impression this was the main problem where the supply authority has changed to supply from TT to TN-C-S then earths also need up-grading have I got it all wrong?
Eric

 

[Spark123]

Not sure where 701 comes into play too - I know that one of the requirements for the ommision of supplementary bonding is effective connection to the MET of all extraneous conductive parts.
The sizing of the protective bonding in TN-CS is relative to the size of the neutral conductor of the supply, in most instances for a 100A supply 10mm² will be sufficient to satsify BS7671:2008 (subject to it being 0.05ohms max) however the DNO should also be consulted as with TN-CS they can overrule this requirement and ask for a larger size to be installed.

 

[ericmark]

Thanks Spark123 for prompt reply I am not going daft then Electrical Safety Council have got it wrong. Maybe they need to remove Safety from their heading and call themselves the "Electrical Near Enough Council"?
Eric