Published: 12 November 2014
Category: Q&A
Julian asks this question, which is about replacing a consumer unit in a TNCS earthed electrical installation, and PME bonding. It has been answered by the NICEIC (Theme – Regulations and Legislation):
This Q & A is one of thousands posted in our Technical Expertise area, and answered on a daily basis by our Voltimum Experts.
Question: Time and time again, when asked to replace a consumer unit in a TNCS installation, I come across main protective bonding to gas and water mains with a 6mm2 bonding conductor.
When I inform the client that it is necessary to increase the size of the conductor, I often get the feeling he/she thinks that I’m inventing work!
When I attended an NICEIC Live event recently, I had a conversation with an engineer who said it was permitted to use the existing 6mm2 conductor – as long as the continuity proved satisfactory.
In your opinion, is that so?
Answer: In Regulation 132.16 of the current Wiring Regulations, it asks that you ascertain that the existing installation is adequate for any for any addition or alteration. This includes the earthing and bonding arrangements.
This does not indicate that it must be upgraded if the existing system is adequate.?
It would need a visual inspection to ensure that no deterioration has taken place, and then reference back to the Regulation that was in place at the time of installation to ensure that it did comply at that time. If all of this is confirmed as correct, then you are able to leave this suitable provision and change the consumer unit.
If this was a new installation carried out under current Regulations, then the size of the earthing and bonding arrangements must be compliant - either by calculation or by reference to the relative tables in the Wiring Regulations.
To see many more Q & A in Voltimum UK's Experts Area, please click on the link. Experts from leading organisations provide online answers to your technical questions on a broad range of subjects. Our searchable database of existing Q & As now contains over 3,500 entries; you can browse through them here.