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tn-s

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  1. 1Justin

    TN-S inadequate earthing conductor

    Hi. I have come across this ~3mm dia earthing conductor soldered to the PE sheath on a TN_S system. Previous electrician replaced the CU and bonding but left this as is. I'm sure it should not have been left this way. Incoming cable looks like a lead sheath and I gather it might be paper...
  2. A

    TN-S or TNC-S

    Hello folks. Need a bit of direction on this one. I went on a survey job the other week, and i need some opinions if the photo shows a TN-S or a TNC-S system? I took a measurment of the Ze, which was 0.54ohms, which suggests a TN-S, but looking at the earth block next to the cut out, there is a...
  3. Tuttle

    2.5mm earthing conductor from TN-S supply

    I found a nice easy second job for my Elecsa assessment. A mate wants an outside light fitting in his porch. He had a new consumer unit fitted last year, all circuits are RCBO protected, and he had a load of other work done at the same time. He's also had some other minor work done since then by...
  4. F

    TN-S system with earth bonding clamp

    Evening Looked at a job tonight, with a TN-S supply. The main earth conductor was 16mm to an earth clamp onto the lead sheathing of the supply. There was a 100amp cut out fuse, with 16mm tails feeding meter and board. The board was updated by a NIC EIC approved contractor only 12 months ago...
  5. J

    Ze on Tn-s

    first time ive came across this so just wondering what i should do? measured a ze of 0.8 on a tn-s so its border line max value is it safe to leave or will it cause issues if left? apologies if its a stupid question, its the silly things that catch you out
  6. La Poste

    TN-S Earth clamp??

    What are your thoughts on this? ELI reads 0.15 Ohms, the lowest I have ever seen but I haven't seen that many. Thanks.
  7. F

    6mm Main Bonding on TN-S domestic install

    TN-S, 60A Main Fuse, 16mm Tails, 16mm Earth. Question - CU change required & at the moment has 6mm Main Earth Bonding to gas & Water, less than 0.05 Ohms continuity measured & good condition. I'm pretty sure that this 6mm size Main bonding is compliant - just thought i would check if i should...
  8. O

    TN-S Earthing

    All Opinions please! I took this photo yesterday while looking at a "new circuit" job, which I'm doing tomorrow. I've not yet done a Ze or Zs but given the bond from the MET to the suppliers bit is clearly old, unprotected and almost certainly under sized would you change the bond or leave...
  9. M

    MAXIMUM Ze at origins of TT, TN-S & TNC-S,

    Hello there, I know this may sound like a daft question but I am currently looking at A job where the Ze reading is 0.37 in a distribution board.It looks to be a TNC-S system by checking where the board is fedd from at the mains cut- out, the run from the mains is about 70 to this board and...
  10. R

    Suppliers Earth TN-S

    Is it ok for you to connect to it ? earth clamp to sheath. I had a call tonight and a customer could not reset his RCD so no power at all.Ok fixed the fault unlpugged the kettle and it reset as soon as we plug it in it tripped so power all restored.Bid disadvantage of having 1 RCD for whole...
  11. P

    TN-C-S or TN-S?

    Hi everyone, Just wanting to confirm something, could you please let me know if these pictures are describing a TN-S or TN-C-S system? Thanks in advance
  12. E

    TN-S or TN-C-S

    Morning all, The earthling arrangements in our house have what looks like a TN-C-S distributors cut out enclosure but has no earth wire where the earth wire should be. Instead there is a small cut-out on the bottom left corner and what looks like 5 or 6 heavy strands of uninsulated copper...
  13. M

    TN-S or TN-C-S?

    Whilst having a quick nosy at my mum's supply I came across a recent installation certificate that was left when her new central heating system was fitted. Before reading the certificate, I was of the opinion it was a TN-C-S supply. However, according to the certificate, they noted it as a TN-S...
  14. P

    Questions regarding TN-S system and RCD

    Hi all, Please excuse an amount of ignorance in this, only 15th ed trained and been out the game for a while. I am currently rewiring my house, with advice from 17th ed but not completed the course yet. We have a TN-s system which at a guess is 40+ years old. Recently our supplyer...
  15. I

    TT or TN-S

    Ok, so we all know what our earthing arraignments are but how would you class this set up and why? Generator feeds an MDU with a 5 core swa (3ph N E). Generator is spiked to earth but feed has earth core to MDU so not relying on terra terra. Although the generator is relying on an earth...
  16. D

    distributers earth above 0.8 for tn-s

    Just tested the Ze at the consumer unit to find it reads 2.47 for a TN-S system. As the lead sheath was so close I also tested with the earth probe directly on the earth sheath, which also gave a high value of 2.44. Replacing the earth clamp on the lead sheath made no difference either. Do I...
  17. BigSi

    TN-S or is it?

    Went to look at a job today. I’m assuming the property is a TN-S system, as there is what appears to be a copper outer sheath over the main incoming cable with an earth clamp on the metal sheath. Never seen this type before, it almost looks like MIMS cable?:confused:
  18. D

    EFL on TN-S with RCD

    I'm doing 30mA & 100mA RCD resting on a TN-S system TN-S earth fault loop impedance max is .8 ohms TT earth fault loop impedance max is 200 ohms Regs state approx 1500 ohms for RCD on TT system What should the maximum Zs be on a TN-S system when testing an RCD?
  19. G

    TN-S and RCD's

    Just done a load of inspections on a caravan park where the entire distribution system is TN-S. Problem is that quite a few of the Ze's are above 0.8 ohms stipulated as maximum. The question is, does the use of RCD's mitigate the above parameter readings? or will they have to get the Ze's...
  20. D

    TN-S Earth

    Hi, can anyone help ar advise on the following. I've just gone to check a dist board for carrying out a replacement, it is a TN-S system. The main earthing conductor is bonded to the supply cable sheath via a standard earth ( pipe ) clamp, of the tenby type. It looks as if the installation...

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