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  1. KeenPensioner

    (r1+r2)/4, the myth expelled?

    Thank you replying. The way I see it is that there are two formula at play here. The recognised formula for resistors in parallel (1/R=1/R1 + 1/R2) and the derived formula for RFCs (R=(r1+r2)/4). Using your own example of 0.3 r1 and 0.5 r2, the recognised formula gives R as 0.225 ohms and the...
  2. KeenPensioner

    (r1+r2)/4, the myth expelled?

    Thank you all for taking the time to respond. "happysteve" in post 23 is agreeing with my original post.....ie the formula does through up discrepancies/variations if the live conductors and cpc are of different csa (as his graph clearly shows)
  3. KeenPensioner

    (r1+r2)/4, the myth expelled?

    Hi, I'm not an electrician but a keen amateur. I understand the testing on RFC and how it's done but couldn't get my head round the (r1+r2)/4 calculation. I've trawled this site (and others) and it seems to me that a lot of people struggle to explain this fully. The truth is that this...
  4. KeenPensioner

    Can't figure ring final r1 + r2 divided by 4

    Figured it out....this image says it all..
  5. why_divide_by_4.jpg

    why_divide_by_4.jpg

    • KeenPensioner
    • Media item
    • Comments: 0
    • Category: Electrical Videos
  6. KeenPensioner

    Can't figure ring final r1 + r2 divided by 4

    Figured it out..see image...attached
  7. KeenPensioner

    Never stop learning

    Never stop learning
  8. KeenPensioner

    Wiring of 5A lighting sockets

    Kuffs.....I like what you say as far as letting people know you are not a qualified sparky. I'm not qualified but have worked as a mate since I retired and have always been interested in domestic stuff. In my experience in the forum, if you are honest and know your limitations you won't get...
  9. KeenPensioner

    Wiring of 5A lighting sockets

    Kuffs.....I like what you say as far as letting people know you are not a qualified sparky. I'm not qualified but have worked as a mate since I retired and have always been interested in domestic stuff. In my experience in the forum, if you are honest and know your limitations you won't get...
  10. KeenPensioner

    Earth fault - potential on exposed conductive part

    Thank you all for your replies, you pointed me in the right direction and I found this.... "The maximum value is R = 50/Ia. Where Ia is the operating current for the protective device in 5 seconds. Ref. 413 - 02 -28. GN3 recommends less than 0.05 ohms.".. . ...it might not be bang up to date...
  11. KeenPensioner

    Earth fault - potential on exposed conductive part

    As can be seen from my profile I am not a qualified electrician but I'm studying in my own time just for the sake of it. I understand the principals of earthing and bonding but in this video by GSH Electrical.... .....at 2:10 minutes in he says exposed conductive parts under earth fault...
  12. KeenPensioner

    Isolating transformer principle

    Lucien Nunes explains it well to me as an amateur. If I get it now the image below shows what I think he means. Thanks again to everyone
  13. isolating_answer.jpg

    isolating_answer.jpg

    • KeenPensioner
    • Media item
    • Comments: 0
    • Category: Electrical Videos
  14. KeenPensioner

    Isolating transformer principle

    Thank you all for taking the time to reply. I've watched almost all of John Ward's videos (on this and other subjects). After reading all your replies and revisiting his videos I think I'm nearer to understanding what's going on. On the "unearthed" secondary winding, rather than thinking of L...
  15. KeenPensioner

    Isolating transformer principle

    Thanks Wilko, but won't one of the "ends" be at 240V and the other at 0V as in the primary winding?
  16. KeenPensioner

    Isolating transformer principle

    Thanks Pete, but I've viewed that from JW and many others...still don't get it! What about the return path in my image?
  17. KeenPensioner

    Isolating transformer principle

    As can be seen from my profile I am not a qualified electrician but I'm studying in my own time just for the sake of it. Everywhere I look for info on isolating transformers I get something like this "This means that the isolation transformer secondary side must not be grounded. It would create...
  18. isolating-transformer_adjusted.jpg

    isolating-transformer_adjusted.jpg

    • KeenPensioner
    • Media item
    • Comments: 0
    • Category: Electrical Videos
  19. KeenPensioner

    Can't figure ring final r1 + r2 divided by 4

    Thanks every body.....I understand it now
  20. KeenPensioner

    Can't figure ring final r1 + r2 divided by 4

    Thank you for your replies......food for thought.......even on a Sunday! I'll study these answers later and get back to you if I still don't get it.

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