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  1. G

    Understanding Earth/Shock

    well wikipedia says resistance of the soil is between 10 - 1000 ohms per meter, so lets say 500 ohms, smack in the middle. Say the transformer is 100 meters away. Ohms law current = volts / resistance, so 500 ohms x 100 meters = 50,000 ohms. I = 230 / 50,000 = 0.0046A 0.0046 amps is not much...
  2. G

    Understanding Earth/Shock

    Hi I am studying to become an electrician. There are a few things I do not fully understand regarding shocks and earth and I cannot find the answers to some of my questions. Can anyone help me understand the following points regarding a standard TN system. 1) If you are in a loft or a 2nd...
  3. G

    Help with CPC size

    Can anyone confirm if the value of t should be 0.01 or 0.1
  4. G

    Help with CPC size

    It is ok, i forgot to square root the value of S
  5. G

    Help with CPC size

    Previous posts must be right, I must be using the wrong value for (t) I read this chart as saying I should use the value 0.01 Other posts say I should use 0.1 I don't see why The current is well over 200A, at which point the breaker would trip in 0.01s ???????????????
  6. G

    Help with CPC size

    I agree the final S value does not seam right, because 6mm cable has a 2.5mm CPC. You should be able to use a smaller CSA conductor than what is recommended, or at least the same. I can't see where I went wrong tho :(
  7. G

    Help with CPC size

    Thank you, don't know how that happened, think it happened when I converted from doc to pdf format, thank you
  8. G

    Help with CPC size

    Think I have corrected the errors
  9. G

    Help with CPC size

    Thank you, I think I have corrected the errors, apart from final S value, it comes out the same every time?
  10. G

    Help with CPC size

    I think I have completed the question. Can anyone find fault with this?
  11. G

    Help with CPC size

    I don't think I could use a 2.5mm CPC so, I used table 4D2A, 2 core cable. There is not much difference anyway and it does not change my results. 47A flat cable with CPC and 46A 2 core cable.
  12. G

    Help with CPC size

    You have a sharp eye for detail.
  13. G

    Help with CPC size

    I get it now, anything times 0 is 0. I guess you just don't factor them in or they must be 1?
  14. G

    Help with CPC size

    Also I think every electrician would just use 10mm2 cable anyway. That way there is room for a future upgrade to maybe a 9kw device
  15. G

    Help with CPC size

    The none impacting factors must be..... Must be what? The graphic supplied does goto 0.01, I drew a green line to indicate the value I was using, I may have covered over the writing with the green line.
  16. G

    Help with CPC size

    You are right, the protective device must be greater than the current flowing. Ib has to be 37. There is no 37 breaker so I guess it should be 40? Thank you for pointing this out :)
  17. G

    Help with CPC size

    You could be right, I may have over thought it. Still it was a good exercise I did learn allot.
  18. G

    Help with CPC size

    Thank you very much I get it now :) I hope you teach, if not you should do.
  19. G

    Help with CPC size

    I think I get it. So as the result was lower than 4mm2, so now I can go back and try again factoring in a 2.5mm2 CPC, if the result is higher I cant use 2.5mm2 I will have to use 4mm2?
  20. G

    Help with CPC size

    Thank you, that is what I thought. My calculations are wrong :(
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