Published: 14 April 2014
Category: Q&A
Don asks this question about circuit protective conductor (CPC) sizing for an electrical installation related to a replacement consumer unit. It has been answered by the NICEIC (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: The electricity company has installed an isolator at a customer’s house before to changing a consumer unit from a wired type to a new twin RCD 17th Edition unit.
The company has fitted new tails from the main fuse to the isolator, and then connected to the original tails to the consumer unit – which are 16mm. The main earth starts as a 16mm from the main fuse and goes to a connector block where it is soldered, and then a 10mm earth cable goes to the consumer unit. The main bonding conductors to gas and water are 6mm.
Is this OK?
Answer: Because you have changed the consumer unit, you must have considered Regulation 132.16.
If the loading has not increased, then what was already in place would be adequate.
The regulation provides earthing arrangement sizing for new installations carried out under the current regulations. If what was originally installed was safe and correct at the time some years ago, then there is no requirement to upgrade - unless additional circuits and loadings are likely.
A visual inspection would have identified any deterioration that would suggest improvement is necessary, but if nothing has changed then there is no need to change this arrangement.
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