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tt system

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  1. S

    mobile home park TT system

    Could you please help me with a couple of queries regarding regulations on a mobile home park? Firstly, what are the site owners legal obligations with regard to additional protection in addition to each home owners RCD? Mobile home parks are fed from a TT system. In other words what protects...
  2. K

    TT System questions

    Have any of you ever come across a TT system that the earth fault loop impedance readings are as good as a TN, TNC-S system? Ie, falling well within the maximum permitted value of the MCB? If so, would you then still recommend RCD protection, If there is none? Cheers
  3. M

    TT System

    Hello All, I am a new member with a question i hope you can help me with. TT System, Ze test with main earth disconnected from earth bar reading = 195 ohms Zs test on ring main reading = 0.68 ohms..! Retested Ze but this time connected to the earth bar (main earth not connected to earth bar)...
  4. C

    TT System Questions

    Hi, at both my colleges TT was only ever briefly discussed and in the main it was TN-S and TN-C-S that was dealt with. The comment tended to be "You'll only ever see that in rural situations". I tried suggesting it's applications in outbuildings even where the main source was TN=S/TN-C-S but it...
  5. D

    How to improve Zs reading on a TT system

    Hi new here :-) Can anyone suggest how I can improve my Zs readings on a TT system for my final cct's. Already have split board with 2 x 30ma RCD's and type B breakers! A Should I be changing to RCBO's? B try adding more earth rods! dont fancy this as problematic... C what can you suggest...
  6. cliffed

    Tt system

    Instaled swa cabling to 2 portacabins,made it tt system,all cabins r tested wiv usual rcd ctrl DBs,problem wiv the Ze offa the earth electode,the measured resistance was 275 ohms,iee recommends max 200 ohms,wot wud you guys do,by the way its a temporary installation cheers men ta ra bab
  7. T

    Nuissance tripping on a 30mA Main RCD on a TT system

    Hi all, hoping some 1 out there can help me on the following problem. just recently qualified and have this nightmare situation with no experience on the following problem. I have nuissance tripping on a 30mA RCD. it trips at random times and can go as long as 5 days before it goes again. the...
  8. D

    TT System

    Sorry guys need help with this one, In 12 years of being a sparks i never come had to deal with TT systems, and for the life of me can remember all the stuff i learnt back in the day and can't find any of my notes from college. CU methods= 1. 100ma (delayed/slugged) main switch, with 30ma...
  9. P

    RCD testing problems on a TT system

    I am testing my garage which has a TT system. I have a 30mA RCD as a main switch but am having problems with RCD testing using my Megger 1720. I have a Ze of 196 ohms which I know is OK so began testing the RCD. When I come to a x5 test it will not test because it tells me I have a touch...
  10. M

    caravan park tt system and earth rods

    Hello everyone, Have been inspecting caravans statics at a 200+site. The levels of ZE are 8+ ohms at the caravan hook up and it is on a TT system (the incomming mains) to 4 or 5 submain distribution points where there is a common earth rod and from there via swa using the cable core or armourmed...
  11. N

    domestic TT system strange fault

    Upon doing a consumer unit upgrade + installation test today I came accross an unusal fault. I did all the usual dead tests and everything was fine, but when doing a Zs on the boiler/lighting/ring main circuits they all came back as reverse polarity. The first thing that came to mind was having...
  12. S

    Help with tt system certification

    HiCan anyone help me with regards to filling in a niceic part p cert with regards to the part were it concerns tt.This is on page 2 I need help with the parts electrode resistance ra , is this the measured ze result I have taken ?And also method of measurement ? Also what is the maximum ze for a...
  13. N

    TT system domestic CU upgrade

    im intending to carry out a c.unit upgrade on a domestic property, no earth provide by supplier so its a TT system,no electrode seems to be visible or present but there is a reading there something like 5ohms could be a buried rod/rods somewhere or connected to old service pipe, going to...
  14. S

    tt system

    hi doing an extention of a tt system via a henely block, 50a fused switch, 16mm cable into a seperate cu. i want to discriminate between rcd's and cu's. my question is do i connect the earth from the 16mm cable into a m.e.t then to earth rod, or just connect it to the fused switch or into the...
  15. L

    TT system scenario - Thoughts please ?

    Massive site in deep rural kent few big dwellings, swimming pool etc etc there is an outer building/shed/store (not sure of use) room on the site as well there has been a seperate feed brought down off the overhead line into this little box built (to house cut outs and meters for all the...
  16. A

    TT system - maximum earth fault loop impedence?

    I've recently completed a part p defined scope course but all of our testing was on TNS or TNCS systems, in our house we have a TT system and in the OSG I can't find much information on the maximum earth fault loop impedence, just says that it is likely to be higher than their TN tables? I might...
  17. G

    High Integrity CSU on TT system.

    If a High Integrity CSU where every circuit is protected by a mix of RCDs & RCBOs is connected to a TT system, is it still necessary to fit a 100mA S front end RCD?
  18. D

    Caravan TT system hook up point.

    Hi i was wondering what the downside to connecting the earth to an earth rod TT system AND to the TNCS from which the supply is being fed from, i understand that in the fault of the pme neutral going down that a caravan could become live under fault conditions but surley 2 earth paths would be...
  19. S

    Disconnection time on TT system

    Can a Sunnyboy SB3800 inverter disconnect on a TT system fast enough to prevent injury through shock? The installation has an RCD fitted and the inverter is connected to a 16 amp MCB. With the inverter having simple separation, does this negate the need for an RCD to protect the cable...
  20. S

    Live earths in a TT system

    Went to put in a new circuit (for a solar inverter) on a property with a TT system (the first time I've encountered one). The existing system is a dog's breakfast with three splits at the after the meter at a Henley block. There's some kind of 60 amp breaker labelled BS 842 in the mix. This may...

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