Posting a message to the forum will remove the above advertisement

Discuss Earth arrangements confusion in the Electrical Forum area at ElectrciansForums.co.uk.

Please make sure you checkout our forum sponsors, many do discounts for members and, they keep the forum free to use.
  1. alan132
    Offline

    alan132 Active EF Member

    Location:
    Essex
    Working on a old property in a slightly remote area installing a new circuit.

    When I looked at the earthing it looked like a tns but I investigated and found a old 2.5mm running towards the rod.

    My problem is I am getting a ze reading of 0.25 ohms.

    Ino we had a really heavy down poor the day before but to be that low?

    I am wait for the dno to confirm the earthing but they ain't rushing.

    Any thoughts
    I know a good reading for tt is 200 ohms or lower. This is the first one I have worked on
     
  2. westward10
    Offline

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

    Location:
    Northamptonshire
    Have you got all main protective bonding disconnected to remove parallel paths. How did it look TN-S for it to then become TT.
     
  3. alan132
    Offline

    alan132 Active EF Member

    Location:
    Essex
    Thats is just the main cable nothing else

    When I manage to peak around the wooden board covering the mains it looked like a swa with a earth strap.
    It's under the stairs and I could hardly fit my head in there.
     
  4. Richard Burns
    Offline

    Richard Burns Trusted Advisor

    Location:
    Cambridgeshire
    Business Name:
    Richard Burns
    If you have an earth connection to the sheath of the supply cable and the Ze reading with all other earthing connection disconnected is 0.25Ω then the supply is TNS.
    If it has a rod connected to the MET then there is an earth rod connected to the MET it would not change the earthing of the supply.
     
    • Like Like x 1
  5. alan132
    Offline

    alan132 Active EF Member

    Location:
    Essex
    As I said I assumed it was a swa.
    But looking out side there was only 2 cables going in.
    So I would say that was a tube of some sort

    This place has had works done but no one has left any certificates

    I will have to contact dno again to comfirm the earth.
     
  6. mhar
    Offline

    mhar Electrician's Arms

    Location:
    devon
    You say it is remote, is it on it's own and does it have it's own transformer? If so is the transformer earthed at the pole?
     
  7. Wilko
    Offline

    Wilko Electrician's Arms

    Location:
    Berkshire
    Business Name:
    Wilko Electrics
    Hi Alan - I've been building up my TT portfolio lately using the larger 5/8" 4ft rods, two at a time. Around here in wet clay this has been good for 10 Ohms or less. I would need to parallel up many many of these to get your numbers, so it's def a DNO means of earthing in my humble opinion. Have you checked Ze against short circuit impedance? Avoid the non trip setting, if you get 0.25 for both then perhaps DNO has PME'd an old TT at some point.
     
  8. alan132
    Offline

    alan132 Active EF Member

    Location:
    Essex
    It's a area they just keep adding to
    There is power pole then when you get to a built up area they stop.

    Can't find a substation near by.

    I don't know if this may affect it but there is a dyke around the place and it on a flood plane
    Ground soft and soak water in
     
  9. mhar
    Offline

    mhar Electrician's Arms

    Location:
    devon
    Properties can be fed from pole mounted transformers not necessarily near a substation.
    There is a method of earthing very occasionally used on single properties in remote locations fed from their own transformer (pnb).
    Have you looked at the pole(s) supplying? If a pme overhead supply there should be a pme label on every third or fourth pole plus you will see an earthing conductor running down the pole.
     
    • Agree Agree x 1
  10. buzzlightyear
    Offline

    buzzlightyear Electrician's Arms

    Location:
    star command
    you are not dowsing for water ,you need to take pic of the set up and show us if poss and speak to dno.
     
    • Funny Funny x 2
  11. Midwest
    Offline

    Midwest Electrician's Arms

    Location:
    Oxfordshire
    Sorry OP for hijacking your thread. Wiko what surveying do you do, if any, when choosing a place to install your earth rods, so as not to hit any other services?

    Just curious as I've not done one yet, and if the 18th has its way, I'd better get some practise in.
     
  12. anthonybragg
    Offline

    anthonybragg Electrician's Arms

    Location:
    NORTHAMPTON
    Business Name:
    CHARLTEC ELECTRICAL LTD
    18th compliance already !.
     
    • Like Like x 1
  13. ruston
    Offline

    ruston Trusted Advisor

    Location:
    Northumberland
    I have a three wire overhead supply from a pole transformer, bare and only the line (live lol) insulated from the last pole to the house. Three houses on this one supply.
     
  14. Phil Thompson
    Offline

    Phil Thompson Let us light up your life! Electrician's Arms

    Location:
    Newtownards
    Business Name:
    Brite Spark Electrical
    I found those rods give a much better reading myself, going to use them from now on.
     
  15. Midwest
    Offline

    Midwest Electrician's Arms

    Location:
    Oxfordshire
    Same question for you Phil;

    Sorry OP for hijacking your thread. Wiko what surveying do you do, if any, when choosing a place to install your earth rods, so as not to hit any other services?

    Just curious as I've not done one yet, and if the 18th has its way, I'd better get some practise in.
     
  16. Wilko
    Offline

    Wilko Electrician's Arms

    Location:
    Berkshire
    Business Name:
    Wilko Electrics
    I think you are right to be concerned as there will always be risks banging in a rod. As we spend a bit of time looking at the existing bonding, I have a go at estimating where I think the services would run from that, look of water connection at property boundary etc. I speak to owner and get their take on where services may be. If I've any doubt remaining, I dig a bit by hand which is the only thing that saved me in the attached pic. The cost of ground penetrating radar hire is £300 or so per day, and probably be about the same if you get a specialist company to do a report on a domestic plot. Folks won't pay for that to have a new circuit in their house, but it's the only way to be sure about what's below.

    20170720_124328.jpg
     
    • Like Like x 2
  17. Phil Thompson
    Offline

    Phil Thompson Let us light up your life! Electrician's Arms

    Location:
    Newtownards
    Business Name:
    Brite Spark Electrical
    Double post
     
    • Like Like x 2
    Last edited: Aug 12, 2017
  18. Phil Thompson
    Offline

    Phil Thompson Let us light up your life! Electrician's Arms

    Location:
    Newtownards
    Business Name:
    Brite Spark Electrical
    I try and opt to locate spike to the rear of a property to avoid any services (here they're always brought from the road/street to the front of a property) and assess drainage and guttering on a property so as to avoid any drainage pipes.

    If frontal location was only option and I wasn't 99% certain I was safe to put a spike down I'd likely have to get further assessment done as whilst a cable finder will locate telephone, virgin and mains etc, water and gas pipes are ran in pvc pipe. So would not show up on any scanner that I've seen.
    Although in general the services are brought the most direct route from street to gas metering equipment/internal stop cock. But not always. Although it's very rare to find them travelling an indirect route here.
    Fortunately it's very rare for me to find TT properties here with no spike already installed, so it's not actually something I have to do very often. That was first this year and only did 2 last year and 1 of those was a new build property in the countryside where all services were visible.

    But common sense and a basic knowledge of how services are routed to properties helps decide.
     
    • Like Like x 1
  19. Midwest
    Offline

    Midwest Electrician's Arms

    Location:
    Oxfordshire
    Thanks for the replies chaps, that was a close en Wiko. My son's having an extension done. When they were digging the footings, they found some unexpected drainage pipes. Thames Water came out and camera'd them, and found another waste pipe. Both were 3' feet down, and if I'd look for a place to put a rod, I'd hit both!

    If this 18th proposal goes ahead, it might prove expensive.
     
    • Agree Agree x 3
  20. Phil Thompson
    Offline

    Phil Thompson Let us light up your life! Electrician's Arms

    Location:
    Newtownards
    Business Name:
    Brite Spark Electrical
    Definitely, Those cable finders are £500 and upwards, but doesn't help with gas and water pipe location.
     
  21. davesparks
    Offline

    davesparks Trusted Advisor

    Location:
    guildford
    With all little bit of planning it should be possible to arrange to use the reinforcing in the concrete as the earth electrode on new builds and extensions.
     
  22. Midwest
    Offline

    Midwest Electrician's Arms

    Location:
    Oxfordshire
    I understand that's the provision. However, if the requirement for earth rod is applied to 132.16, and I'm putting an extra socket in an old terraced house in the town centre, it's going to be difficult and not cheap.
     
  23. anthonybragg
    Offline

    anthonybragg Electrician's Arms

    Location:
    NORTHAMPTON
    Business Name:
    CHARLTEC ELECTRICAL LTD
    If I stand corrected I thought the draft said on the lines of preferably. I think that they will accept that when you go around to Mrs Muggins house to fit an extra socket it would not be practical to go and run earth cable outside to a earth electrode.
     
  24. Midwest
    Offline

    Midwest Electrician's Arms

    Location:
    Oxfordshire
    Reg 542.1.201 .........Additionally, there shall be an earth electrode, supplementing any earthing facility provided by the distributor, in accordance with 542.2.3 (which describes earth foundations).

    Still not quite clear on this draft reg, perhaps I (and others have read it incorrectly?)
     
  25. Wilko
    Offline

    Wilko Electrician's Arms

    Location:
    Berkshire
    Business Name:
    Wilko Electrics
    Oh dear - "shall" has no wiggle room in it ... let's us hope there's a clause somewhere that can keep up from this one's grasp.
     
    • Like Like x 3
  26. alan132
    Offline

    alan132 Active EF Member

    Location:
    Essex
    Back to my post.
    Should of mention the service head is 2 separate connection blocks

    And there is no earth coming off the neutral.

    2 cables come in from the roof stright to the service connections
     
  27. wirepuller
    Offline

    wirepuller Trusted Advisor

    Location:
    south uk
    I'm confused having just read this thread....first it was a possible TNS with a strap on the sheath....now it's two singles coming in overhead?
    Am I missing something?
     
  28. alan132
    Offline

    alan132 Active EF Member

    Location:
    Essex
    Yh I couldnt confirm it then later I explain it was a tube that the cables come through
     
  29. westward10
    Offline

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

    Location:
    Northamptonshire
    Any chance of a picture.
     
  30. alan132
    Offline

    alan132 Active EF Member

    Location:
    Essex
    Will have to get one when I go back.

    IMG_20170811_201826_412.jpg
     
  31. westward10
    Offline

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

    Location:
    Northamptonshire
    What is the supply, the lower swa. Can you show more.
     
  32. telectrix
    Offline

    telectrix Scouser and Proud of It Trusted Advisor

    Top Poster Of Month

    Location:
    cheshire/staffordshire
    Business Name:
    Telectrix
    bigger pic would help.showing where all them cables go to/come from.
     
  33. wirepuller
    Offline

    wirepuller Trusted Advisor

    Location:
    south uk
    The lower SWA is an outgoing circuit......the incoming supply is top left of the pic and is not completely shown. There appears to be a braid connected to the MET, where does that go?
     
  34. alan132
    Offline

    alan132 Active EF Member

    Location:
    Essex
    That white unit is what I have just installed

    The service blocks are from the overheads

    The earth cable goes to a metal pipe that has the service cabless in then a 2.5mm cable goes to the ground where a earth rod is

    View attachment 20170822_132348.jpg
     
Loading...
Similar Threads - Earth arrangements confusion Forum Date
Backbox earth points Electrical Wiring, Theories and Regulations Sunday at 10:37 AM
Should I use 1mm or 1.5mm earth in domestic lighthing? Electrical Wiring, Theories and Regulations Thursday at 8:31 PM

Share This Page

  • Electricians Directory Post a Domestic Job Post a Commercial Job