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110v industrial sockets

bakey1959
I have come across some 110v industrial sockets (BSEN60309) which are installed in a utilities company's premises and which are not installed as Reduced Low Voltage (RLV) as detailed in BS7671.
I do understand that the RLV is required for constructions sites and similar premises due to the method of connection of the secondary which had a Line to Earth voltage of 55V.
The ones I have encountered have the Earth pin of the yellow 110v sockets connected to the primary earth, and when tested at the sockets there is 110v Line to Earth, and there is no connection of the Earth pin to a centre tapping of the double wound 240/110v transformer.
My thoughts are that, although the premises is not actually a BS7671 section 704 location, it does actually present similar hazards that might be encountered on a building site, and that having decided to install 110v sockets, presumably for safety reasons, why would you not ensure they were RLV where I believe there are no known incidents of electrocution?
I cannot find any guidance in the Safety First Best Practice Guide as to if a Classification code should be applied, but I am thinking that as an absolute minimum, the client should be informed in writing of the situation.
What do others think?
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  • 0

    I do understand that the RLV is required for constructions sites

    I'm not sure it is, at least from a BS 7671 perspective. It's an option certainly and in most circumstances a very good one - but there are others - including LV plus 30mA RCD protection. Most of the 230V world manages with 230V hand held tools and RCDs (a bit like fused plugs, RLV is rather UK peculiarity). The HSE might well prefer RLV too, but we're getting a bit outside BS 7671 then. Worth a mention to the customer certainly, but be aware that there are other possibilities.

       - Andy.

  • 0 in reply to AJJewsbury

    Thanks Andy.

    Yes, at the moment it does fit the alternative of LV plus 30mA, but the fact that someone has gone to the trouble of fitting a 5kVA transformer and 110v socket outlets makes me think that the intention would have been to go for the 55v to Earth option (CTE) and the protection against shock that that brings?

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  • 0 in reply to AJJewsbury

    Thanks Andy.

    Yes, at the moment it does fit the alternative of LV plus 30mA, but the fact that someone has gone to the trouble of fitting a 5kVA transformer and 110v socket outlets makes me think that the intention would have been to go for the 55v to Earth option (CTE) and the protection against shock that that brings?

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  • 0 in reply to bakey1959

    Quite possibly - or they might just have wanted the ability to use the same tools they use elsewhere on RLV systems. Certainly worth raising with their safety elf.

    One other thought - is it definitely a single phase transformer? There is a 3-phase version of RLV that has 110V between lines and therefore around 63V L-PE - which might account for you seeing something well in excess of 55V L-PE. Off load it might be somewhat higher than 63V - although I wouldn't have expected it to be that close to 110V.

       - Andy.

  • 0 in reply to AJJewsbury

    Thanks for the follow up. It is definitely 240v single phase and the Line to Earth is close to 120v off load. I get your point that, maybe they 110v that is used on construction sites where there is RLV, and would want to use it in their away from site premises, but for the minimal difference in cost why would you not specify a CTE transformer with the enhanced safety benefit, I can not see any practical reason?

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