James asks this question, which is about inadequate cabling provision for a three-phase distribution board, and what the correct solution would be. 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: I’ve just carried out a site survey during which I discovered a 300mm x three-core SWA cable run from the main switch panel, a length of 100 meters or more to a three-phase distribution board.
When I asked the site’s in-house electrician how he had a three-phase distribution board run off a three-core cable (with no visible neutral), he explained how, as it was only a small neutral current, he had run a small SWA cable to the local lighting and power distribution board 10 meters away and picked up the neutral there.
I have raised the question as to how severe this situation is and have now been tasked with rectifying the problem. If a single-core armoured cable was to be run in parallel with the 300mm x three-core submain cable from the same source at the main switch panel, am I right that the correct solution would be to replace the 300mm x three-core cable with a 300mm x four-core type and bring the neutral conductor within the armouring, therefore alleviating possible eddy current issues?
Answer: Indeed, you are right, the regulations do not allow the neutral to be run separately. It should be contained inside the same enclosure as the phase conductors and, therefore, a replacement supply would need to be put in place.
The arrangement needs to be put right, as this provision is inadequate.
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