Graeme Grant asks this question, which concerns a risk assessment for connecting a circuit into a 200A three-phase PDU, and whether the neutral bar is classed as a ‘live part’ or not. It has been answered by the NICEIC (Theme – Regulations & Legislation):
Question: I've been asked to write a risk assessment for connecting a circuit into a 200A three-phase power distribution unit (PDU - data centre). The PDU cannot be isolated for business reasons. The protective devices are 32A BS88 pull out fuse links. The neutral bar is exposed within the cable way along with the earth bar.
Am I correct in saying that the neutral bar is classed as a 'live part', and therefore, the task of connecting to the neutral bar is 'live working'?
Or is it just that the neutral cable of the circuit being installed is classed as a live conductor, and therefore, I can connect to the neutral bar without isolating it?
Answer: Regulation 537.1.2 - The neutral conductor need not be isolated in a TN-S or TN-CS supply if it is in accordance with the Electricity Safety, Quality and Continuity Regulations 2002, which means that it can be considered to be reliably connected to earth by a low impedance.
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