When is a TN-C-S connected socket not permitted?

27 Jan 2008
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Llanfair Caereinion, Nr Welshpool
United Kingdom
We have sockets for garden equipment which is in the main class II, so no problem, although today battery and petrol powered devices have in the main made them redundant. However for 3 days a year we have for example a wagon mounted steam organ which needs a supply, which in turn supplies their caravan, and it seems we in house use 110 volt (55-0-55) but the brick transformers connect the supply earth to the output earth, so the 110 volt supply is still TN-C-S.

I am not that worried, as there is so much metal in the ground with the metal framed buildings that I can't ever see the TN-C-S reaching anywhere near the 50 volt limit to real earth, but should we get a HSE visit would it be picked up?
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Doesn't the same 'argument' apply to any 110volt tool/device fed via an extension lead coming from a 55-0-55 transformer who's earth point is inevitably connected to the 240 service supply earth - TNCS or otherwise. The 110 extension lead implying the end user is some distance away from the supply building

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