GN8 Chapter 6 Extraneous-Conductive-Parts and their connections Equation 6.1

In Guidence Note 8 where the equation 6.1 is used to illustrate the range of values of resistance RCP for the currents IB of 0.5mA, 10mA & 30mA in equations 6.2, 6.3 & 6.4, what is the second value of 1000 thats deducted from the value of RCP for? Looking at equation 6.1 the first value of 1000 thats deducted is for the impedance of the human body ZT taken to be 1000Ω from BS IEC 60479-1:2018 for the purpose of this calculation, but I'm struggling for this moment to understand what the subtraction of the second value of 1000 is for?

It looks to me like the equations have been incorrectly printed and the sum of each should be 459,000Ω, 22,000Ω & 6670Ω respectively and the second value of 1000 should be dividing the sums by 1000 to convert the values to KΩ?

If this is the case then these equations have been miss printed and miss represented in GN8 for the last 20+ years! Not to mention the publications and documents that they've been copied across to over these years...

Any thoughts on this would be much appreciated...

Parents
  • It never ceases to amaze me the direction a discussion can head from the original post and I thank all whom have taken their time to contribute. I shall certainly be taking some of this new found knowledge and information with me for future use and knowledge sharing...

    I'm very much enjoying the banter and the trip down memory lane all the way from BODMAS to BIDMAS and even PEMDAS, is that really a thing? Who would have thought that there were errors in the SI system. I would have thought that the SI System was as flawless as BS7671 & GN8 ;0)

    Did someone actually manage to get Trigonometry into the discussion also? Brilliant :0)

    I had a lovely Almond Croissant with a Cappuccino this morning whilst delivering my Tech Talk on the omission of supplementary bonding in a location containing a bath or a shower.

    The one thing that I shall definitely take away from this and be putting to good use immediately is what Mapj1 typed 'Measure with a micrometre, cut with an axe' love it :0)

    I do appreciate all that has been said, I really do, but I still think that the worked example equations (6.2, 6.3 & 6.4) could be written to give better clarity for everyone at all levels.

    We don't need to have a copy of Equation (6.1) at the start of each worked example. The wording above the worked examples eludes to the fact that Equation (6.1) is used.

    And then the repeat of the equation, but with the bracketed part worked for us, why?!

    I've had a go at re-writing it myself after considering all of the comments and would again appreciate your opinions. I've even managed to chuck a couple of comas in...

    How complicated can we make Ohms law look! That's not a challenge BTW ;0)

Reply
  • It never ceases to amaze me the direction a discussion can head from the original post and I thank all whom have taken their time to contribute. I shall certainly be taking some of this new found knowledge and information with me for future use and knowledge sharing...

    I'm very much enjoying the banter and the trip down memory lane all the way from BODMAS to BIDMAS and even PEMDAS, is that really a thing? Who would have thought that there were errors in the SI system. I would have thought that the SI System was as flawless as BS7671 & GN8 ;0)

    Did someone actually manage to get Trigonometry into the discussion also? Brilliant :0)

    I had a lovely Almond Croissant with a Cappuccino this morning whilst delivering my Tech Talk on the omission of supplementary bonding in a location containing a bath or a shower.

    The one thing that I shall definitely take away from this and be putting to good use immediately is what Mapj1 typed 'Measure with a micrometre, cut with an axe' love it :0)

    I do appreciate all that has been said, I really do, but I still think that the worked example equations (6.2, 6.3 & 6.4) could be written to give better clarity for everyone at all levels.

    We don't need to have a copy of Equation (6.1) at the start of each worked example. The wording above the worked examples eludes to the fact that Equation (6.1) is used.

    And then the repeat of the equation, but with the bracketed part worked for us, why?!

    I've had a go at re-writing it myself after considering all of the comments and would again appreciate your opinions. I've even managed to chuck a couple of comas in...

    How complicated can we make Ohms law look! That's not a challenge BTW ;0)

Children
  • And that is a version I do fully agree with ;-)  Please don't be put off by the way,

    in the manner of 'Look what they've done to my post, ma' as Melanie Safka might have sung, but she didn't, quite.

    Discussions on here do sometimes do this sort of thing, and it is ( to me at least) this free flow train of thought stuff that makes it interesting-  all of us learn something, even if it is only what  is not obvious to others and maybe how to better explain it.

    Further the most innocent questions are often the best at that...

    M
    PS the measure with micrometer and axe thing is not originally mine but part of a Hewlett Packard application note, though right now the exact one eludes me. - and it might not actually have been HP..

    The original was

    Measured with a micrometer

    Marked out in chalk

    Cut with an Ax.

    (A spelling I abhor actually but there we go, they are quite a successful former colony....)

    PPS PEDMAS is a thing see here

    and it seems that  posters are made to hang up on American classroom walls

    Yours for 20 dollars plus postage, laminated I presume