Julian asks this question about replacing a consumer unit in a TNCS installation and the required size of the bonding conductor. It has been answered by the ECA (Theme – Distribution Equipment including Cable Management):
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 6mm2 bonding conductor.
When I inform the client that it is necessary to increase the size of the conductor, I often get the feeling that they think I’m inventing work!
I recently had a conversation with an electrical engineer who said it was permissible to use the existing 6mm2 conductor if continuity proved satisfactory.
So, in your opinion, is it permissible, safe and satisfactory to not increase the main protective conductor to gas and water mains?
Answer: The size of the bonding conductors should ideally be increased to comply with the current requirements.
However, if the client doesn't want it done, and if the conductors are in good condition, the 6mm2 bonding conductor may be left as it is during a consumer unit change.
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