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tt system

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  1. Z

    MET on a TT system?

    Going to do a consumer unit change and earthing upgrade on tt system for my coming assessment in two weeks,straight forward enough.. all earthing straight to the consumer unit..untill i look in the IEE ELECTRICIANS GUIDE TO THE BUILDING REGS..which shows a main earthing terminal, and 16mm to...
  2. T

    tt system

    doing a rewire for registration with elecsa, main earth looks about 2.5mm or 4mm? goes outside and sunk in concrete driveway sheathed but not protected. my question is do i have to replace if my readings are fine? can i protect cable in conduit to overcome changing? don't fancy digging up...
  3. E

    Faulty RCCB on old TT system

    I have a problem to sort out - it is a TT system with a faulty 80A 10mA RCCB after the meter and before the consumer unit. The board is very old style MCBs with no RCDs present. The customer called me up because until about 6 weeks ago the front garden lights were causing the RCCB to trip. I...
  4. 1

    A little assistance please Re: TT System, 0.21 ohms on Earth Rod.

    Good afternoon everyone, I'm just looking for a little friendly advice if I may. I have been to a property to price up installing an Extractor fan (via lighting circuit in Bathroom) and a FCU for a combi boiler. Before work was due to commence I noticed that the Main Earth was completely...
  5. B

    TT system

    hi all. I am after some advice and i cannot find an answer in the regs. I have undertaken a job around a family members where the garage is being converted into a guest house. Its a three phase supply too the house and a TT system. I have run an armoured too the garage too a single phase...
  6. G

    Can a 30mA RCD be used as the sole means of fault protection for a TT System?

    Hi all, went to a job today to price up an shower install, it was a TT so as i was leaving i decided to do a quick check on the main earthing conductor as i could not see earth rod pit outside house, i had a look inside db and could only see 2 x 10mm earths which i assumed are gas/water...
  7. T

    High Ze on a TT system - help for a newbie please.....

    I was called out to replace a couple of pendant fittings and install a fused spur for an extra socket into a cupboard. Installation done, all dead tests were fine, but live tests came up with a Ze of 806 ohms. Zs was similar figure. 30mA RCD (within timings for x1 and x5) fitted before entering...
  8. T

    tt system low pfc?

    hi all, haven't posted for a while, but i have been here - reading and learning. i'm hoping to get a little advice on a low pfc i've come across. a mate has been extending his bungalow, and wants the full rewire. i've gone to have a look, and i've basically done pre work checks to assess the...
  9. marksparky

    max zs on a tt system

    hi folks was wonderin if u have a tt system with a ze of say 113ohms, and a circuit say lights with a r1+r2 of 1.33ohms, in the section on test results were it asks max zs allowed by bs7671.... the answer for a type b 6amp mcb would be 6.13. So if my zs is ze..113+ (r1+r2)1.33 =114.33 which is...
  10. J

    TT system bad earth help

    Hi, My question is as follows - I have recently gone to a site to replace some lighting, and before I started I noticed the fuseboard/Earth were in a bad condition so I carried out a Ze test before starting works. With all parallel paths disconnected and just the earth electrode I got a...
  11. VoltzElectrical

    ZS on a TT system

    What do we do about testing for ZS on a TT system? sorry, but never covered this in college. I know Ze should be below 200 ohms, and that the max Ze can be 1667 to give disconnection time when covered by 30mA RCD. But I've never given thought to actually testing and certifying a TT installation...
  12. T

    6mm main earth on tt system

    6MM MAIN EARTH on a tt system with 100 ohm ze at db ,it runs under patio to rod .do i have to upgrade it as it means patio has to come up ? old wylex 6 way rewireable fuse board protected by old crabtree 60amp elcb i have to add a spur for a stannah stair lift and upgrade the non existing...
  13. E

    Multiple Electrodes, distributed TT system

    I've just started work to "upgrade" an old installation, which also involves taking out some earlier sub-standard work. Basic description: Rural farm house & outbuildings - overhead single phase supply - 3 phase transformer on pole in adjacent field. Supply arrives in an outbuilding, from...
  14. C

    help selecting best inverter for tt system 4kw

    hello all, struggling to find the right inverter for this job.its our first one with a tt supply.we usually use sma 4000TL on these size jobs,but i can't see a way of satisfying manufactures 100ma max rcd and current regs. to my mind,a transformerless inverter doesn't seem suitable for a tt...
  15. robd

    TT system inspection pit

    Afternoon all, Can anyone tell me if there's a reg stating you need to use inspection pit/box/cover or whatever you want to call it for the main earth rod/rods or is it just good practice. Thanks
  16. S

    Very Hi ZS Reading on TT system? any advice

    Hi guys, i have changed a fuse board today in a outbuilding/large shed (it has a kitchen and shower and lounge etc.. a ) It is a TT system with earth rod. My ZE reading was 187 ohms - now the regs state I am ok upto 200, so I assumed this was ok. All the R1 + R2 and insulation resistance...
  17. W

    Rcbos in a tt system

    is there anyone who can clarify the debate about single pole rcbos on a tt system??? i have a main 300mA s type DP rcd at origin and wanted to use rcbos on sub main cu's in other buildings instead of using a single 30mA device to protect a whole cu as a whole board going down would be an issue...
  18. K

    TT system and Zs results

    Just finishing off cert for a TT system, got a Zs of 115 ohms throughout. will I be right in thinking the max Zs column for all circuits will be 1667 or 200? Cheers
  19. cashnotakite

    TT system but no RCD as main switch

    hi, need some help with this one; I'm testing a board that is TT but doesn't have an RCD as main switch, it has a standard 100A switch disconnector (60947-3). However, every circuit in the installation is RCBO protected. Is this ok? Just to make matters a little more awkward the supply cable...
  20. J

    connect caravan to TT system

    Hello I need connect caravan to CU in house with TT system. I have got 10mm 3 core SWA cable. Do i need separate earth electrode for caravan, or connect armour and 3th core to CU in house ? Distance from house to caravan is 15m.

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