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Looping Lighting feeds at switches in singles

Baldyhugh
Hi

A few months back I posted a question regarding different methods of connecting lighting feeds and switch feeds at switches in singles conduit cable. My question was more from an eddy current perspective. I’m currently working on a job with steel trunking where the drops to switches and sockets etc from the steel trunking are in plastic conduit and the switches / sockets are plastic. My previous post queried whether having just live / switch live and earth down through a single hole in the trunking to the switch or live/neutral/earth supply to switch and live/neutral/earth out to the light through a single hole in the steel trunking was acceptable. I opted for the latter. My question now is can I take a permanent feed to the next switch from the previous switch? In effect I’ll have l/n/e supply to switch and l/n/e to the light and l/n/e to the next switch, so 9 cables at the switch position all through a single hole in the steel trunking. I know this method is used in domestic settings with t&e cable but singles in conduit has the flexibility of running each single cable directly where it needs to go but from an eddy current perspective having all my single cables through the single hole in the metal trunking down to the switch gives me peace of mind. Thanks in advance
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    davezawadi (David Stone):

    These currents are part of a circuit. This is as Broadgauge says exactly the opposite so there is no significant field. His point about EM fields is nonsense, many of us would be severely damaged if this were true, particularly those having NMR scans, the danger is from heating if anything, and this needs very high frequencies and high field strengths. There are detectable effects on Haemoglobin (blood contains iron atoms) for example but have never been shown to be dangerous. A single cable with magnetic material does cause eddy currents, but the heating effect at low current is negligible at 50Hz. The regulations are rather vague about this, probably could do with clarification and revision.


    I agree that the alleged health effects are nonsense, and was therefore careful to use the word "alleged" in my post.

    However not everyone agrees and some allege all sorts of ill effects.


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  • 0
    davezawadi (David Stone):

    These currents are part of a circuit. This is as Broadgauge says exactly the opposite so there is no significant field. His point about EM fields is nonsense, many of us would be severely damaged if this were true, particularly those having NMR scans, the danger is from heating if anything, and this needs very high frequencies and high field strengths. There are detectable effects on Haemoglobin (blood contains iron atoms) for example but have never been shown to be dangerous. A single cable with magnetic material does cause eddy currents, but the heating effect at low current is negligible at 50Hz. The regulations are rather vague about this, probably could do with clarification and revision.


    I agree that the alleged health effects are nonsense, and was therefore careful to use the word "alleged" in my post.

    However not everyone agrees and some allege all sorts of ill effects.


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