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P.M.E. and Potato Peelers.

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About 2 years ago I was asked to undertake electrical work at a local chip shop/fast food outlet. I was concerned about large metal drummed wet potato peeling machines located on a wet floor in an old outbuilding and the P.M.E. earthing system. I could not devise a safe system in my mind where the large potato peeling machines positioned on a wet stone floor could be made safe with the P.M.E. earthing.


Anyway, unfortunately recently the place burned down and is now boarded up. The cause may not be electrical, but due to oil catching fire.


I have not done any work in the building at all.


Because the machines could not be effectively TT earthed I did not proceed with any work.

https://www.edp24.co.uk/news/norfolk-norfolk-fire-at-mundesley-business-7985784


Z.
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  • 0
    Zoomup:
    whjohnson:

    I just winder if there is too much paranoia surrounding the loss of a neutral in a PME system in a built-up area. Maybe different out in the sticks, but with local substations being relatively plentiful in urban areas what is really the risk?


    You could well be right.  Lower risk than we perceive perhaps. I was going through a concerned phase at the time. The 14th edition used to require that single phase sockets on different phases be kept at least 2m apart. Was there really a risk if single phase appliances were supplied by sockets on different phases? What were the real life reported accidents?


    Z.







    Back in the days of unearthed lighting circuits I suspect that the risks were significant.

    An unearthed brass light switch or pendant lamp holder was fairly low low risk in an office or factory with wooden floors.

    However two such switches or lamp holders and connected to different phases (or poles of a DC supply) and within reach would be dangerous.

    Hence the old regulation of one pole or phase per room, with an exception for large rooms where this was impractical, in which case different phases or poles of a DC supply were permitted if 6 feet, later 2 meters apart.


    The general use of plastic lamp holders and light switches  and the earthing of lighting circuits rendered the regulation pointless, and it was removed, correctly in my view.


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  • 0
    Zoomup:
    whjohnson:

    I just winder if there is too much paranoia surrounding the loss of a neutral in a PME system in a built-up area. Maybe different out in the sticks, but with local substations being relatively plentiful in urban areas what is really the risk?


    You could well be right.  Lower risk than we perceive perhaps. I was going through a concerned phase at the time. The 14th edition used to require that single phase sockets on different phases be kept at least 2m apart. Was there really a risk if single phase appliances were supplied by sockets on different phases? What were the real life reported accidents?


    Z.







    Back in the days of unearthed lighting circuits I suspect that the risks were significant.

    An unearthed brass light switch or pendant lamp holder was fairly low low risk in an office or factory with wooden floors.

    However two such switches or lamp holders and connected to different phases (or poles of a DC supply) and within reach would be dangerous.

    Hence the old regulation of one pole or phase per room, with an exception for large rooms where this was impractical, in which case different phases or poles of a DC supply were permitted if 6 feet, later 2 meters apart.


    The general use of plastic lamp holders and light switches  and the earthing of lighting circuits rendered the regulation pointless, and it was removed, correctly in my view.


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