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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
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    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
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    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
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    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.
     
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  5. Ian1981
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    Ian1981 Electrician's Arms

    Location:
    North east
    The email says an earth reading 0.44 ohms no?
     
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  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
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    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
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    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
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    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
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    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
    Online

    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
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    Ian1981 Electrician's Arms

    Location:
    North east
    IMG_2885.PNG
     
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  16. Ian1981
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    Ian1981 Electrician's Arms

    Location:
    North east
    IMG_2887.PNG
     
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  17. AdamGiguere
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    AdamGiguere Guest

    The cut out does not come with the earth brass bar as shown above the 25mm earth comes from elsewhere - I'll have to investigate further.

    As there must be a problem with the earthing connection?

    Just baffling as to why the DNO have not picked this up, would they have just done the test between L-N?

    Surely not?
     
  18. AdamGiguere
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    AdamGiguere Guest

    The MET is just screwed on next to the cutout
     
  19. Ian1981
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    Ian1981 Electrician's Arms

    Location:
    North east
    Any pics?
     
  20. AdamGiguere
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    AdamGiguere Guest

    Not of the origin - I should have. Apologies...

    I'll question the DNO tomorrow when I call.

    I'll have to return to the site. There must as you mentioned be something wrong with the earth connection but I couldn't for the life of me see anything wrong earlier when I was looking....
     
  21. westward10
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    westward10 In echoed steps I walk across an empty dream. Electrician's Arms

    Location:
    Northamptonshire
    If they are telling you it is PME and you are getting those readings then you have no link between the earthing conductor and supply neutral.
     
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  22. westward10
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    westward10 In echoed steps I walk across an empty dream. Electrician's Arms

    Location:
    Northamptonshire
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  23. Ian1981
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    Ian1981 Electrician's Arms

    Location:
    North east
    And I thought my garage was a mess;)
     
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  24. AdamGiguere
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    AdamGiguere Guest

    Yes that's what it would seem right.

    There must be a problem with the link but just wondering why the DNO have not picked this reading up....?

    Would they have just tested between L-N ?
     
  25. westward10
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    westward10 In echoed steps I walk across an empty dream. Electrician's Arms

    Location:
    Northamptonshire
    Possibly you need to get back in touch with them.
     
  26. AdamGiguere
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    AdamGiguere Guest

    I'll call them tomorrow, shall let you know the outcome...

    Many thanks for all your responses - most appreciated

    Adam
     
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  27. Wilko
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    Wilko Electrician's Arms

    Location:
    Berkshire
    Business Name:
    Wilko Electrics
    Hi - from their wording, they have provided you with a PME means of earthing. However given the 9 Ohms Ze, it seems it's not been connected to the installation's MET (by you :) )
     
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  28. Davisonp
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    Davisonp Regular EF Member

    Location:
    Amersham
    Business Name:
    Absolutely All Electrical LTD
    I cannot see anywhere that it states that the property is currently a PME system. In fact, the OP says “the 25mm earth comes from elsewhere - I'll have to investigate further” so it looks like it is currently a TT or TNS system. The DNO actually seem to be saying they made a decision to provide PME tails for an electrician of choice to connect into the excising setup. I suspect they have not done this yet and will do the actual conversion when an electrician is present.

    Are you sure this is not a TT system?
     
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  29. buzzlightyear
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    buzzlightyear Electrician's Arms

    Location:
    star command
    a thingamabob you put a fuse in .
     
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  30. westward10
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    westward10 In echoed steps I walk across an empty dream. Electrician's Arms

    Location:
    Northamptonshire
    Just reread all this and you are quite correct. OP where does the 25.0 earthing conductor go to I probably wrongly assumed it went to the head.
     
  31. AdamGiguere
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    AdamGiguere Guest

    Hi Davisonp

    This sounds like a good translation of their wording.

    I'm pretty sure it's not a TT system/although could be mistaken.

    I did think perhaps maybe a TNS due to the 0.44 on the L-N

    But have been advised by a colleague who came to site with me originally that it's a TNCS.

    Hopefully they have a log of their visit and can advise what system it definitely is
     
  32. westward10
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    westward10 In echoed steps I walk across an empty dream. Electrician's Arms

    Location:
    Northamptonshire
    Is there no earthing conductor from the service head.
     
  33. AdamGiguere
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    AdamGiguere Guest

    No there isn't possibly could be a TNS then...as I do believe it going out of the meter cupboard and into trunking which then goes in to the ceiling of the porch area....
     
  34. AdamGiguere
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    AdamGiguere Guest

    In future I'll always be getting detailed pics I appreciate all your time guys!!!

    Great forum!!
     
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  35. Des 56
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    Des 56 Trusted Advisor

    Location:
    Gliese 581C
    I thought it was only myself that was confused so i refrained from posting anything
    Having read the later replies it appears to me I am not alone

    Op,can you give a definitive description of the head and the supply type
    Is there a separate earth conductor entering the property?

    Can you confirm or deny a installation earthing conductor connection has been made
    to the Pme at the cut out or elsewhere even?
     
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  36. AdamGiguere
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    AdamGiguere Guest

    Will retrieve pics and post ASAP...I've asked the tenant (family friend) to take a pic or two of the meter cupboard
     
  37. westward10
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    westward10 In echoed steps I walk across an empty dream. Electrician's Arms

    Location:
    Northamptonshire
    They need to go outside and see if a green/yellow wire drops down the wall.
     
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  38. AdamGiguere
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    AdamGiguere Guest

    I'm pretty certain it doesn't...

    If it did it would be unnoticeable/covered from sight...
     
  39. AdamGiguere
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    AdamGiguere Guest

    If there was no link - would I be getting a reading similar to 9 ohms?

    I'd expect no reading...?

    If so and there is no link - where is the 9 ohms coming from?
     
  40. westward10
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    westward10 In echoed steps I walk across an empty dream. Electrician's Arms

    Location:
    Northamptonshire
    We need a clearer picture of what is going on because this has become very confused. I think I wrongly assumed the earthing conductor was connected to the head hence my assumption there was no link to this conductor from the supply neutral.
     
  41. buzzlightyear
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    buzzlightyear Electrician's Arms

    Location:
    star command
    .
    but reading between the lines i think it is TT supply,read post 1 (tested at supply pole)
     
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  42. AdamGiguere
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    AdamGiguere Guest

    I did think this when reading it - supply pole would indicate earth rod...

    But if this is the case then they have said 0.33 at the supply pole, I shouldn't be getting a reading of over 9 ohms at the MET should I?
     
  43. soms
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    soms Trainee Access

    Location:
    Somerset
    Are you measuring the Ze with all earthing and bonding conductors connected to the MET? This could result in your 9 ohm reading through an earth path formed by some other extraneous-conductive-part(s)?
     
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  44. buzzlightyear
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    buzzlightyear Electrician's Arms

    Location:
    star command
  45. buzzlightyear
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    buzzlightyear Electrician's Arms

    Location:
    star command
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