tt system

tt system

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  1. B

    TT system do I need to fit a main switch or time delayed RCD switch?

    Hi everyone I'm ready to do second fix on a rewire it's a tt system all my circuit will protected by individual rcbos Do I need main switch to be normal dp switch or time delay rcd please help.
  2. F

    TT System Existing is a multi9 13 way RCD main switch DB

    Hi Ive read a few discussions on the topic but what setup would you recommend for replacing a DB on a domestic TT system? I've moved house and need to get the meter changed ready for the car charger, I need to upgrade the severely dated DB at the same time. Existing is a multi9 13 way RCD...
  3. U

    TT system EICR questions

    Wondering if anyone can advise as I’m struggling to understand the regs, I’ve never tested or even worked on a TT system. I have tested an old farm that has been converted to a school so it is no longer an agricultural premises. The main supply is a three phase PME which feeds all 6 consumer...
  4. C

    Inverter - TT System issue

    Hope this all makes as much sense as i can make of it and my "problem" can get sorted via some guru on here... Just a quick background on myself, i am fully qualified and have been for 15+ years. I have completed the 18th edition and am a member of the approved and domestic installer schemes on...
  5. N

    TT System High Ze leading to possible Zs fails

    Doing a lot of EICRs at the moment and have came across what I'm sure is a common enough problem. In an off grid rural cottage I have a TT system, Diesel Generator that runs and charges batteries when they are below 10 percent or so. Ra is about 150 Ohms... was about 3 ohms for Ze before main...
  6. T

    Seperate test sheet for garage consumer unit on a TT system

    Hi Guys, hopefully someone will know the answer. Testing an install on a (domestic) PME system I have a garage consumer unit supplied from one of the RCBO's I have installed an earth rod to supply the earth and not connected the CPC or armouring to the garage consumer unit end. My question is...
  7. I

    TT System with TNS reading

    Shop with no earth coming from head, overhead lines in sight everywhere - definitely no earth from the DNO. Two 10mm earths going into the DB. One going to the water and another which disappears through a wall somewhere heading towards an external area never to be seen again. Customer doesn’t...
  8. cliffed

    TT System with Upgraded DB/CU

    Big argument with a newly qualified electrician with all the necessary qualifications Had to give him a hand later on during the day, nice DB fitted &to be fair quite tidy too , with SPD…It’s a TT System with a good Ze 24.8 ohms. All Rcbo’s except for the Mcb supplying the SPD, which I pointed...
  9. I

    Three phase equipment RCD protection on a TT system

    TT system, existing three phase fuse board recently installed by another spark which only has single phase circuits terminated into individual RCBOs Required to install three phase circuits for new equipment, is there a better way of doing this than fitting a 4pole RCD ahead of the main switch...
  10. J

    MCBs ADS in TT system

    Quick Question. Despite being 50 I am a newbie electrical installer. Preparing for my retirement from public service. Anyways - my Question. How the hell do MCBs work on a TT system. Say Ze is 33 Ohms with a 240 supply the PFC will be just over 7 Amps. How does that trip MCBs or is there were...
  11. Raptor0014

    Advice regarding isolator for 3ph TT system

    Morning all, I’m scratching my head with this and granted I don’t do a lot of commercial work. Hence I thought I’d ask. Setup is a pub with a 3ph supply and it’s TT So it goes Incoming head - 3 x 100a cutout Meter 3 pole isolator for L1, L2 & L3 L1 to single phase into plastic DB L2 to...
  12. Raptor0014

    Correct Type-S Upfront RCD for 3Ph TT System

    Hi all, Doing an EICR on a property which is 3Ph in and then 3 x Single phase boards from that. However it's on a TT System and doesn't have a upfront 100mA RCD and I am not aware of any reason why one wouldn't be required. So I am just wondering if this MCG one will suffice into an enclosure...
  13. S

    UK Consumer unit TT system far from DNO fuse

    Evening all, I’d appreciate your opinions here: I’m looking at an old (150 years+) stone house. Complete rewire and renovation. DNO fuse is currently where the master bedroom will be (upstairs). Client wants it to be moved to a more accessible location downstairs about 15m away depending on the...
  14. J

    Curious DNO MET on TT System

    Just completed an EICR which had an Unsatisfactory Report done earlier in the year by another Spark, i have a copy of the report and he's put the earthing system down as a TN-S and a ZE of 0.21. However as you can see the main earthing conductor (16mm) doesn't go to what appears to be a DNO MET...
  15. S

    EICR 100ma RCD TT systems

    Good Morning all , Carrying out an EICR yesterday on a domestic property TT system , which is not a system I frequently work on. My question is that I have a Plastic CU, All circuits protected by RCBO’s, Satisfactory main protective bonding in place & A Good ZE / PFC well within the limits of a...
  16. F

    TT SYSTEM

    Took a swa cable to an outside metal shed, earthed at house end but insulated at shed end. Installed earth rods and got reading of 58ohm . all good. However glanded cable shed end for experiment and got 0.24ohms. Question what are the dangers and why cant you have both earthing systems in...
  17. S

    RcD x5 failure on TT system

    Hi Guys, recently installed a new radial socket circuit from CU. When ramp testing 30ma RCD at unit, without loads, everything was fine. When I energised the circuit and tested again, the furthest two sockets failed the x5 test giving a 40ms reading. Other sockets on the same circuit came in...
  18. S

    Advice on TT system

    When carrying out Ze with main earth disconnect I get a reading of 77.25 ohms. All good. When main earth is reconnected and all parallel paths in place reading comes down to 0.60 ohms. I have 3 lighting circuits not covered by an rcd all Zs readings are well in permitted Zs. Would any body apply...
  19. I

    TT system, earth to neutral not tripping RCD

    TT system, Zs on socket circuit is 77.2 down a good bit after I added a second earth rod. When I short neutral to earth RCD doesn't trip. Can anyone help me out and explain please.
  20. S

    How do I comply TT system

    Hi guys wondering what's the best way to do this got a board change on a TT system 3 bed terrace. So we need to offer an SPD however can't have one in a metal C.U without RCD protection on the Tails because of the single insulation feeding the SPD. So to do that that we need an s type RCD...

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