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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
    Offline

    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
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    telectrix Scouser and Proud of It Trusted Advisor

    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
    Online

    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
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    telectrix Scouser and Proud of It Trusted Advisor

    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
    Offline

    jlrb EF Member

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

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

    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 Trusted Advisor

    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
    Offline

    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
    Offline

    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
    Online

    Murdoch Electrician's Arms

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