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Discuss TNCS High ZE at origin in the Electrical Forum area at ElectrciansForums.co.uk.

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  1. AdamGiguere
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    AdamGiguere Guest

    Hi there

    Testing at origin of a domestic property, I have found:

    L-N: 0.44 Ohms
    L-E: 9.89 Ohms

    I had the DNO attend clients address, there response was that it was quite high and confirmed readings of 0.44 for ZE. (Pleasee attached document with their response)

    My concern is they don't seem to have checked the reading between L-E......

    Anyone know what could be the cause of this? MET connections are tight and in good condition....

    Many thanks in advance.

    Adam

    IMG_3970.PNG
     
  2. westward10
    Online

    westward10 In echoed steps I walk across an empty dream. Electrician's Arms

    Location:
    Northamptonshire
    I am a bit confused have they now made it TN-C-S with a Ze of 0.44.
     
  3. AdamGiguere
    Offline

    AdamGiguere Guest

    Hi Westward10

    No they have not done anything...

    L-N still reads 0.44 (but as all circuits are protected by rcd's isn't so bad)

    But L-E is far too high.....
     
  4. westward10
    Online

    westward10 In echoed steps I walk across an empty dream. Electrician's Arms

    Location:
    Northamptonshire
    If L/N measures 0.44 so should L/E on a PME system. Why does their letter indicate an earth reading of 0.44, is this were you are deeming as being high.
     
    • Agree Agree x 3
  5. Ian1981
    Online

    Ian1981 Electrician's Arms

    Location:
    North east
    The email says an earth reading 0.44 ohms no?
     
    • Agree Agree x 4
  6. AdamGiguere
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    AdamGiguere Guest

    They haven't mentioned about the L-E reading which is why I'm a little concerned as I'm aware the highest should be recorded....

    But in any case the L-N and L-E readings should be more or less the same for TNCS...

    I'm just wondering what could be the cause of the high ZE on L-N...

    The only thing I can think of is the earthing connection could be damaged somewhere.

    Perhaps an earth rod would fix.
     
  7. AdamGiguere
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    AdamGiguere Guest

    They have mentioned this yes, however any board I test L-E at I get Ze of about 9 ohms, the same as when I test Ze at end of circuits I get 9 ohms.

    I will call them tomorrow but I'm sure they'd have checked both L-N & L-E surely.

    If so why am I getting 9 ohms...baffling me...
     
  8. Ian1981
    Online

    Ian1981 Electrician's Arms

    Location:
    North east
    well it's the pen conductor getting tested so if your testing at the consumer unit L-E it would be the same result more or less as testing L-N unless the earth connection going into the cut out needs attention giving you a high impedance
     
  9. westward10
    Online

    westward10 In echoed steps I walk across an empty dream. Electrician's Arms

    Location:
    Northamptonshire
    I have had this on PME where there is no connection to the supply neutral. So to clarify you have 0.44 L/N and 9.00 P/E?
     
  10. Wilko
    Offline

    Wilko Electrician's Arms

    Location:
    Berkshire
    Business Name:
    Wilko Electrics
    Reading the OP note from DNO, they have provided PME at 0.44 Ohms. They expect the Electrician to connect to the new PME tail and confirm you now have Ze of 0.44 and that it is sufficient to meet ADS in the installation.
    Have you done that?
     
    • Agree Agree x 5
  11. AdamGiguere
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    AdamGiguere Guest

    Correct....
     
  12. AdamGiguere
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    AdamGiguere Guest

    Stuggling with their wording and action to be taken. When they say

    When they say provide new PME tails what do they mean exactly...?
     
  13. ImpededLoop
    Offline

    ImpededLoop Electrician's Arms

    Location:
    West Sussex
    You'd be best to go back to site and have a look. If you're unsure, take a few pictures and post them on here.

    Let us know the outcome either way.
     
  14. AdamGiguere
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    AdamGiguere Guest

    When you say the "cut out" what do you mean?

    Understand the N and E are one in the same more or less but need to sign off the work but at each point measuring Ze (L&E) it's far to high -
     
  15. Ian1981
    Online

    Ian1981 Electrician's Arms

    Location:
    North east
    IMG_2885.PNG
     
    • Like Like x 2
    • Agree Agree x 1
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