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  1. B

    Ze=1.87 TT or TN-S?

    Morning all, Looking for some opinions MK Sentry Dual RCD 63/30 CU Fluke 1662 readings... 2 lead hi current Ze= 1.87 Ohms PEFC = 6A PSCC = 0.774kA 3 Lead no trip Ze = 12.95 Ohms Zs at cooker/sockets = 12.56 RCD times are compliant No electrode visible and Gas & H2O 10 mm at board...
  2. P

    When TN-S is TN-C-S

    On another thread there was chat about the N-E voltage to be expected, so I decided to measure my flat out of curiosity as it appears to be TN-S. A brief history - my flat is a Victorian built 4+4 arrangement and when I moved in many years ago each flat was fed by MICC cables. Something like a...
  3. C

    Earth Rods in TN-C-S and TN-S

    Why aren't earth rods required on a TN-C-S or TN-S supply? In the US earth rods are mandatory for both. Two earth rods if the first one is over 25 ohms. Here is how its typically done: View: https://youtu.be/4vxYXzNtE9A?t=3459 #6 copper (13.3mm2) is run from the neutral bar of the first...
  4. Andy-1960

    TN-S vs TNC-S (PNB) Earthing System

    What are the thoughts of you guys on the differences between a TN-S and a TNC-S (PNB) Earthing System. My understanding is as follows: TNC-S (PNB) - the Neutral & Earth Conductor are joined in the main switchboard with the neutral conductor between the transformer and the switchboard then...
  5. M

    Earth clamp for TN-S lead sheath supply cable

    Hi Does anyone know where you can purchase the earth clamps that the DNO use on their lead supply cables? I used to have a few but cant find them anymore and Im not sure of the correct name for them. Cheers Martin
  6. J

    After some advise please- Tn-s earth arrangement

    Evening all, Just after some info on the photo attached. It’s a tn-s system with an Earth going to the cu met from under the floor boards. After lifting the boards I found the earth attached as so... I was expecting to see a clamp around the supply cable, not a choc block with legs of unknown...
  7. TonyJohnson

    TN-S or TN-C-S From this photo

    Hi, I undertsand this to be a TN-S system as the earthing arrangement comes along the SWA metal sheath surround but the Ze i got is 0.19 which falls out side the regs of 0.8. Chameleon Electrical -...
  8. B

    TNS system or not what do you think?

    Hi guys Shouldn’t this have an earth? I’ve tried to add a picture but to be honest I’ve no idea how lol Thanks
  9. J

    Domestic Possible problem with supply earth connection on TN-S system

    Long time reader, first time poster. We moved house about a year ago and had an EICR carried out before purchasing. Everything checked out fine but with a some C3 recommendations for improvement. The power supply to the house comes up through the floor in the cupboard under the stairs...
  10. J

    Opinion on Supply System Type Wanted: TN-S or TN-C-S

    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...
  11. L

    Standby Generator Earthing (TT or TN-S)

    Hi Everyone The utility supply for an installation is of TT system. The Generator start point is connected to the its frame and earthed to an electrode. Thus, the installation has its own earthing electrode. I would like to know whether the installation is a TT or TN-S system when the standby...
  12. A

    RCCB 100a type s on a TN-S

    i come across this today and it does not sit well with me. so im after a little advice. its a TN-S system Ze 0.12 and Zsdb 0.16 there a type S 100A rccb as a main switch with no RCD's up stream, This does not sound right to me and all the MCB's are C type. all my I.R were greater than 2k except...
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