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Safe Disconnection to Undertake Work.

Zoomup
Scene. An old farm building now used as a double glazing frame maker's workshop.


The supply comes from an old shed about 40 metres away, where the meter is. The old shed has some 70s/80s rusty M.E.M. isolators that feed several S.W.A. cables that exist the shed in many directions underground. I suspect that one feeds the main farmhouse, another a rented cottage and the others various farm buildings. There is no clear labelling of the isolators.


What is the best way to locate the frame maker's  building supply where I have to work?


Somewhere I have a circuit i/d set, if I can find it, but that will need access to the live parts and I do not wish to turn off the wrong isolator.


Z.


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  • 0
    AJJewsbury:
    That is interesting kfh, What astounded me though was that the main three phase cut out has two S.P. Henley blocks placed side by side connected to Neutral, by the main fuses. They are linked together with a very short length of 16mm2, or imperial equivalent, cotton covered single cable. These two Henleys are used as earth terminals. How does that date things Watson?

    I've seen setups like that in rural areas (or more likely both N and PE into one Henley block) - often PNB rather than PME though.

       - Andy.


    There is a single black cable running from the Henleys down 

    into the ground, possibly about 16mm2.  The supply is from  newish A.B.C. overheads.



    Edit. Add. So Andy, are you saying that the earthing of the Neutral is at the installation head position only and not at the supply transformer star point? Is that P.N.B?


    2nd Edit. Add https://www2.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=47661&STARTPAGE=4&FTVAR_FORUMVIEWTM


    The PNB discussion is very long and convoluted.


    Z.


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  • 0
    AJJewsbury:
    That is interesting kfh, What astounded me though was that the main three phase cut out has two S.P. Henley blocks placed side by side connected to Neutral, by the main fuses. They are linked together with a very short length of 16mm2, or imperial equivalent, cotton covered single cable. These two Henleys are used as earth terminals. How does that date things Watson?

    I've seen setups like that in rural areas (or more likely both N and PE into one Henley block) - often PNB rather than PME though.

       - Andy.


    There is a single black cable running from the Henleys down 

    into the ground, possibly about 16mm2.  The supply is from  newish A.B.C. overheads.



    Edit. Add. So Andy, are you saying that the earthing of the Neutral is at the installation head position only and not at the supply transformer star point? Is that P.N.B?


    2nd Edit. Add https://www2.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=47661&STARTPAGE=4&FTVAR_FORUMVIEWTM


    The PNB discussion is very long and convoluted.


    Z.


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