Our Voltimum Experts answer your questions on a daily basis in our Technical Expertise area. This one, concerning final circuit wiring and conductor CSAs, is answered by SELECT:
This is then split into five parts. My question relates to the installation of dado trunking for supplying IT equipment and twin and earth (T&E) wired ringmains. At present we install with twin & earth cable, dual earth socket outlets, and use two protective conductors terminated separately throughout the whole installation. Therefore we install as (iii) - two individual protective conductors, each complying with the requirements of section 543.
Where the two individual protective conductors are both incorporated in a multicore cable, the total CSA of all conductors, including the live shall not be less than 10mm sq.
Does this mean that by using 2.5mm T&E on a ringmain, we are not complying - as I assume that T&E is classed as a multicore and the total CSA of each cable would be 2.5 + 2.5 + 1.5. Would this mean that we would have to install ringmains using 6.0mm T&E so that the CSA is over 10.0mm or, by installing a ringmain and effectively using two multicore cables, this is sufficient?
Answer: Regulation 543.7.1.3 deals with final circuits and distribution circuits. Regulation 543.7.2 deals specifically with final circuits supplying socket-outlets.
It sounds as though you are complying with the regulations, providing that you are connecting the CPCs as per Regulation 543.7.1.4, and that notices are provided as per Regulations 543.7.1.5 and 514.16.
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