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  1. Baddegg
    Offline

    Baddegg Still simmering Ken, not boiled yet buddy x Electrician's Arms

    Location:
    Portsmouth
    As per a couple of previous threads am now at first fix stage and am thinking about testing,
    Set up is tn-s,main income tails split through Henley into switch fuse isolater and 10mm 3 core sea out to (approx 20mtrs) Cu unit in man cave/pub
    Never tested a unit so far from the origin that wasn’t a sub db, questions are is this still considered a sub board? Am I right in thinking I need to take ze at the origin before switch fuse isolator? As to take it at the Cu is not external? And if so what would I record on the sheet for the swa feeding the unit?
    Hope that makes sense?
    Thanks in advance as always
     
  2. Andy78
    Offline

    Andy78 Forum Mentor

    Location:
    Kingston upon Hull
    A reading at the CU would be the Zs of the distribution circuit feeding that CU.
    A Ze is taken at the origin with the installation isolated and all parallel paths removed.
     
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  3. Grezza
    Offline

    Grezza Active EF Member

    Location:
    Liverpool
    The CU feed is a final circuit so as above, remove all PP and test at incoming.

    I’d also test at the CU and record as a Zdb and note where it was taken from.
     
    • Like Like x 1
  4. Baddegg
    Offline

    Baddegg Still simmering Ken, not boiled yet buddy x Electrician's Arms

    Location:
    Portsmouth
    Thanks chaps, I’m fine with ze at origin etc just with why the shed Cu becomes a final/distribution circuit as opposed to a normal Cu,is it just because it’s more than 3 mtrs and the isolator has been introduced?
     
  5. Andy78
    Offline

    Andy78 Forum Mentor

    Location:
    Kingston upon Hull
    Any loop reading within the consumers installation will be a Zs, be it at the end of a final circuit or distribution circuit. I'm not sure what you mean by "normal CU" and how any other CU would differentiate with the one in this shed.
     
  6. Archy Styrigg
    Offline

    Archy Styrigg Electrician's Arms

    Location:
    Manchester
    Is the CU in question fed from the Switch fuse? If not, surely it needs some protection being >3m.
    Where do the other tails go to?
     
  7. Baddegg
    Offline

    Baddegg Still simmering Ken, not boiled yet buddy x Electrician's Arms

    Location:
    Portsmouth
    Hi Archie yes unit in question is fed from the switch fuse,the other tails go to the Cu in the house as per original set up
     
    • Like Like x 1
    Last edited: Nov 6, 2018
  8. Baddegg
    Offline

    Baddegg Still simmering Ken, not boiled yet buddy x Electrician's Arms

    Location:
    Portsmouth
    Sorry Andy, I’m starting to confuse meself here,normal Cu being any standard household unit less than 3 mtr tails, where you’d take your ze as per normal, I’ve tested sub db’s before that have been feed through an mcb on the household unit and understand why they are considered final circuits, as this setup (the unit in the man cave) is on its own after the switch isolator it’s caused me to think a bit more about I how I record my readings and where I take them from,
     
  9. Andy78
    Offline

    Andy78 Forum Mentor

    Location:
    Kingston upon Hull
    Not half as confused as I am.

    Back to original post

    Any circuit that feeds a distribution board is a distribution circuit.
     
  10. Andy78
    Offline

    Andy78 Forum Mentor

    Location:
    Kingston upon Hull
    Yes.
     
  11. Baddegg
    Offline

    Baddegg Still simmering Ken, not boiled yet buddy x Electrician's Arms

    Location:
    Portsmouth
    Thanks Andy
     
  12. ChrisElectrical88
    Offline

    ChrisElectrical88 Forum Mentor

    Location:
    Norwich
    Ze at Origen.
    Zdb at Dist Board.
    Switch fuse to be treated as its own board on the certificate. Dist board will be the circuit from this switch fuse so R1+R2 IR etc will need to be taken on the sub main.

    If that makes sense
     
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  13. Baddegg
    Offline

    Baddegg Still simmering Ken, not boiled yet buddy x Electrician's Arms

    Location:
    Portsmouth
    Perfect thanks Chris,
     
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  14. ChrisElectrical88
    Offline

    ChrisElectrical88 Forum Mentor

    Location:
    Norwich
    So on your Circuit schedule your circuit will be call for example 'Submain to DB - DB1' and filled out and tested as any other circuit.
     
    • Like Like x 1
  15. Murdoch
    Offline

    Murdoch Electrician's Arms

    Location:
    Woking
    Interesting read ....... so the origin is the DNO fuse? No - so the Ze to be taken at the Henley block?
     
    • Like Like x 2
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