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tt system

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  1. Strima

    Fire Alarm Circuit RCD Protection TT System

    Doing a board swap on a HMO property with a TT system later this week and I've been asked to add OCPD for an L1 fire alarm system. As usual the landlord is being a little cagey with letting me know the other tradesmans details so I can confirm this but I'm on the understanding that a fire alarm...
  2. C

    RCD Main switch on TT system

    Hello everyone, Does an RCD as main switch in a TT system a must or not? My question is can you use an isolator and then RCDs for the rest of the distribution board? Thank you
  3. J

    UK Installing a sub main from existing TT system

    Hi all, I’m new here and after some advice on a sub main circuit I have a 3 core SWA feeding a log cabin from a house. The house has an existing TT system and I’m just wondering what the best way to supply the log cabin would be? What would I need up front to protect the SWA, I’m presuming a...
  4. T

    Best Consumer Unit set up for TT system

    Hi all, I'm just wondering what is people's preferred choice of set up with regards to DB's for a TT system within a domestic setting. I know there's different views on this (Type S uprfront etc). Are most people installing dual rcd boards or DP Rcbo's? Just looking for some views on this. Many...
  5. S

    TT system

    Hi guys the house I live in is a the earthing arrangement is a TT sytem were the meter is outside the house I opened up and saw there was no met terminal with no earth. I remember when the house was built there was an earth rod buried in the ground my question is was the earth suppose to be run...
  6. L

    Coding for lack of 30ma rcd protection - TT system

    I’ve had a disagreement with a colleague on this. Installation has 100ma rcd main switch. Some circuits (5) on this side and further 4 on the 30ma rcd side. what is the coding for this?
  7. T

    TT system testing

    Hi everyone. A recent install I've done on a tt system is giving me a reading of 93.3ohms as a Ze reading. When I then test from my circuits inside I'm getting readings like 106.3 for a socket circuit supplied from 32 amp type b mcb (which should be no higher than 1.10 ohms in bs7671) anyone...
  8. M

    TT system

    Evening gentlemen, TT System, previous spark fitted new metal CU. I’ve got an outbuilding to wire, it’s fed by a 10mm swa. I’m going to be putting in a time delayed 100ma RCD before the main CU. The swa feed to the outbuilding cu will be fed via a switched fuse. My question is, do I split the...
  9. B

    TT System RCBOs/RCD

    Hi All Trying to do some digging on TT systems. With regards to TT systems, I have had different views/opinions on this stating that TT installations should have double pole RCD when it comes out of the meter so the installation is protected by RCD before tails enter in consumer unit. I also...
  10. S

    TT System Consumer unit/RCD Arrangments

    HI All, Wondering what the best configuration is for a Consumer unit replacement on a TT system. is a 30ma Split load board with a 100ma time delayed RCD as the main switch suitable in todays standards? do you completely remove the red double pole main switch and replace with a double pole...
  11. HappyHippyDad

    Would I still need a gland for the tails and earth on this TT system?

    The installation is TT. The meter box has been moved by the DNO. The tails will now be >3m so I will be fitting a switch fuse. I was planning on removing the DP switch in the switch fuse and replacing with a 100mA S type RCD. I would have put one in place of the main switch in the CU so this...
  12. B

    TNS, TT SYSTEM

    Got a question (this job is done), Mains is TNS, now there is an SWA from mains that feeds a panel, now I’ve tested this site a few times and readings vary for some reason, now to be safe feeding a new panel which will be outside then to some outdoor sockets, the panel (with upfront RCD) is fine...
  13. cliffed

    Protection on Tncs / tt system

    Pme Swa sub main supplying external tennis courts. Because of cable size,tt system will be installed. The original Pme supply comes from main distribution area,from a Bill Switchfuse isolator,63 amps. The new tt system is ze 13 ohms,the Pme earthing system is 0.35 ohnms. No connection to the Pme...
  14. M

    TT system eic minor point

    New circuits. Ra of 229 Ohms therefore the rcds are for fault protection by design. Zdb of 0.29 (10mm gas bond) so are the rcds classed as additional protection?
  15. Michael J

    The maximum value for Zs on a TT system is 50/I delta. So for a 30mA RCd is 1667 ohms

    why is this not the case if the final circuits on a TN-S or TN-C-S system are protected by a RCD? Funny what you think of when you can’t sleep
  16. P

    TT system - Reg 411.5.1

    Just looking at the second part of this reg with the statement " The neutral point or the midpoint of the power supply system shall be earthed. If the neutral point or midpoint is not available or not accessible, a line conductor shall be earthed" My question is... I assume they are talking...
  17. Bobby34

    TT system, RCD or RCBO

    At the risk of asking a silly question could someone advise me on the following: Client has a TT system with only half the circuits covered by an RCD, they want a light adding on a light circuit thats currently not covered by the rcd. Now with half circuits not going to meet the disconnection...
  18. B

    Caravan site readings on TT system

    Hi, have a distribution unit which feeds some caravan boxes TT system, it has upfront 300mA RCD and double pole 60898, now I’ve been sent to re gland as the disconnect times wasn’t met, but I’m getting readings of 0.30 ohms when max is either TT 167 ohms or if you go by MCB then 0.59? But the...
  19. R

    Supply to summer house TT system

    Hi all , this is my first post , i’m a qualified electrician but I spend my whole time sub contracting to a factory installing and moving machinery so i’m a bit out of touch ( although taking the 18th on may 3rd ) with domestic work! A friend has asked for a supply to his summer house so I took...
  20. B

    Swa armour feeding TT system

    I have installed a TT system at my garage, and it is fed via 10mm 2 core armoured cable, does the armour of the cable have to be earthed via the supply tncs side or can it be glanded and earthed the garage side (TT). Anyone know the regs ? Thanks

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