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tt system

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  1. P

    How to get a TT system upgraded to TNC-S

    Hi I have just rewired a mate’s house with his help and the existing earthling is TT on overheads. We have tried to get it changed to PME (TNC-S) but who do you contact now a days. Back when I did nothing but house bashing in was a piece of cake, now its been split up they keep sending bods...
  2. G

    TT system and earthing

    Would appreciate some advice please. I'm wiring a TT system and am un-sure of what earthing is required. Reg 411.3 - 'Requiremnts for fault protection', says that protective equipotential bonding is required to extraneous-conductive-parts which i'd already done. Am i correct in saying that there...
  3. R

    100 mA rcd on tt system?

    HI, I've been asked to do a pir on a domestic installation, Means of earthing is a TT system using a 100 mA (not s-type) rcd as the main switch, covering all circuits. House is a rental property...Is there any real problem with this with regard to regs? would appreciate any advice thanks.
  4. H

    sMaximum earth loop impedance for TN systems, and TT system

    I am finding this quite a complicated subject, and I would really welcome your thoughts on this subject. If I could start with a TT system, according to regs, 411.5.3 states that when using an RCD for fault protection purposes, then the following has to be applied. RaxIn<=50 This means that...
  5. P

    TT system earthing reading - Help ?

    Hi all, What safe readings should I get for earthing a TT system in a domestic property ? Thanks Phil.
  6. G

    TT system testing - problem

    Hi, can anybody throw some light on a problem / confusion i have? I'm in the process of installing a new TT system. The existing earth electrode had a high resistance in excess of 2Mohms. I've inserted a new electrode in a new location and measured the resistance immediately after inserting the...
  7. S

    TT System Query

    Good Morning I would like some advice. Working on a Domestic TT System. Primarily a kitchen refurb. The customer in my case is the contractor. I told him there should be an earth electrode around. I tried to locate and could only locate 6mm earth cable to a disused lead water pipe...
  8. V

    Low ZS on a TT system

    Hi guys, I've got a TT system with a Ze of 21 ohms. Two ring final circuits are on the same rcd and are both giving a Zs of 1.7 ohms - does this indicate a neutral - earth fault?
  9. sparks1234

    TT system

    I am quite interested to know how people would go about this installation. Install a 3-phase supply from a house to the middle of a field and install a distribution board with main switch. approx 150 mtrs Then from one phase run away to various outlets for caravans the furthest being 300 mtrs...
  10. E

    Size of cable to earth rod - TT system

    Hi all, Quick question, can you use a 25mm cable from earth bar in C/U to Earth Rod in cellar directly below? Reason I ask is I need the 3m tails to extend from incoming fuse, and they come with a 25mm earth cable included, so would this be easier than running a new 10mm earth cable to the...
  11. V

    TT System MET??

    Could the MET for a TT system be an earth bar in a garage CU? This would then feed the house CU (opposite side of attached garage wall) earth bar using 4mm conductor. All loads are 30ma RCD protected. Thanks
  12. G

    earthing for tt system

    can anybody help me, a mate of mine has a tt system at home and asked me to test his house as he wants to rent the property. i would just like to no what size earth should it be for a tt system, at the moment its 6mm and without diging me books out am not sure if it requires upgrading and knew...
  13. J

    6mm earthing on a TT system

    hi all i ahve been reading up on tt systems am i correct in saying that a tt system can have a lower earthing conductor than a tncs or tns? can anyone explain why? and also what is the lowest earthing size u have seen on a tt system ?
  14. C

    low psc reading on tt system

    Hi Recently come across a submain installed in a property that had a 63 amp d type mcb and a 100ma s type rcd as its overcurrant and earth protection. Fair enough. I measured a psc of 558 amps. Voltage 248 amps Ze 128 ohms. At origin. As an mcb is designed to operate in .1 of a second would...
  15. W

    TT System and 30mA RCD tripping times

    Help! Sorry having a bad day. I understand the concept behind touch contact of 50v and the above 1666 ohms. But when physically testing with 17th ed dilog and testing a TT system 30mA RCD. At 1x and 5X what reading would you see on your meter? or would you just test the mechanical aspect...
  16. W

    tt system

    If a TT system has been put under ground is it still classed as a TT system and still need the 100ma RCD at the origin
  17. P

    tt system rated tripping current of RCD

    guys, been to a house this after noon which is on a tt system. Found that the man rcd before the board has a rated tripping current of 500ma was wondering if this is correct as cannot find it in the regs also is it right that you can only do a half reading and a x 1 reading on this unit.(rcd...
  18. R

    Outbuilding supply from TT system

    I am wiring an outbuilding, to be used as an office at the moment. I am nearly at the stage of running the supply out to it from the main house. The main house has a TT supply. Would the correct way to do it be to use a 63a 100ma time delayed rcd to protect the swa supply, and 30ma protection...
  19. P

    Zs values on TT system

    Hi guys new to testing and about to do my first TT system tomorrow. Popped in today and did a quick Ze test and got 16.98 ohms. Zs values will not meet max values for 7671. Whats your thoughts guys. (what have I forgotten?). Pete
  20. O

    converting outbuildings to a tt system

    some asked me about why earthing a garage has to be a tt, ill be honest, i new it had to be done but i couldnt remember why, i knew it had something to do with neutral current but someone enlighten me please

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