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Discuss Opinion on Supply System Type Wanted: TN-S or TN-C-S in the New Member Introductions area at ElectrciansForums.co.uk.

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  1. jlrb
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    jlrb EF Member

    Location:
    London
    Hi - My first post to this forum.

    I am having a disagreement with another electrician on the type of the supply characteristics for a domestic installation, i.e. whether it is TN-S or TN-C-S. I have uploaded a photo of the cutout/supply head. To resolve the disagreement I suggested we ask for a 3rd, 4th, 5th .... opinion from the forum.

    The building is in a suburban area and is over 100 years old , not that I am suggesting that the supply head is that old. There are no PME labels/markings. The measured Ze is 0.11 ohms.

    Thanks for your views in advance.

    jlrb

    Supply Type.jpg
     
  2. Lee42
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    Lee42 Lee

    Location:
    England
    I would say TN-S
     
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  3. telectrix
    Online

    telectrix Scouser and Proud of It Respected Member

    Location:
    cheshire/staffordshire
    Business Name:
    Telectrix
    only DNO could tell you for sure . rare to see supply in split concentric.
     
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  4. Murdoch
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    Murdoch Electrician's Arms

    Location:
    Woking
    Did you test L-N fault loop?
     
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  5. Lee42
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    Lee42 Lee

    Location:
    England
    Did you have to remove the seals to gain access?
     
  6. jlrb
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    jlrb EF Member

    Location:
    London
    Yes that is what I though - however when I called UKPN they said that they do not have information on supply type. Go figure! So no help there.
     
  7. telectrix
    Online

    telectrix Scouser and Proud of It Respected Member

    Location:
    cheshire/staffordshire
    Business Name:
    Telectrix
    measure both pefc and pscc. if they are the same, i'd opt for TNC-S.
     
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  8. jlrb
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    jlrb EF Member

    Location:
    London
    No, the seal was already broken.
     
  9. telectrix
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    telectrix Scouser and Proud of It Respected Member

    Location:
    cheshire/staffordshire
    Business Name:
    Telectrix
    :eek::eek::eek::eek::eek:
     
  10. jlrb
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    jlrb EF Member

    Location:
    London
    Thanks - that was my thought on next step too if there isn't a barrage of consensus from the forum. Even then it will still be an inferred result which I was hoping to avoid.
     
  11. telectrix
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    telectrix Scouser and Proud of It Respected Member

    Location:
    cheshire/staffordshire
    Business Name:
    Telectrix
    you could always dig up the supply cable and see where the earth is. :(
     
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  12. jlrb
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    jlrb EF Member

    Location:
    London
    Ha ha - I bet the DNO would love that!
     
  13. Vortigern
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    Vortigern Electrician's Arms

    Location:
    England
    Business Name:
    F.H. Electrical
    TN-S
     
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  14. jlrb
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    jlrb EF Member

    Location:
    London
    As Murdoch and telectrix suggested:

    Measured PEFC = 2.10 kA (0.11 ohms)
    Measured PSSC = 1.30 kA (0.18 ohms)

    This indicates to me that it is TN-S rather than TN-C-S, but I was expecting the relative values to be the other way around - but on reflection I am not sure why I should expect that.
     
  15. Murdoch
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    Murdoch Electrician's Arms

    Location:
    Woking
    My "guess" would have been TN-S..................
     
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