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BS7671 Amendment 4. Sidebar markers

JohnE

I have the Bronze digital subscription package

I've noticed that the online edition does not have the vertical marker lines
on the right hand side of the page to highlight a change from the previous editions.
I have been informed that the lines are in the gold subscription.


Any ideas why
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  • 0

    I wouldn't feel too left out if I were you ... even in the printed version the side bars seem not to quite have the value they should have.

    Many show only stylistic differences (e.g. "r.m.s." changes to "RMS") while others seem to appear where I can see no changes at all.

    Most worrying there seem to be some small but significant changes (e.g. > changing to ≤ in A722,3) which aren't indicated at all (in that case I suspect it's just a correction of an earlier error, but it's still a change from the previous published version as far as I can see).

       - Andy.

  • 0 in reply to AJJewsbury
    AJJewsbury said:
    Most worrying there seem to be some small but significant changes (e.g. > changing to ≤ in A722,3)

    That must be an error.

  • 0 in reply to AJJewsbury
    Chris Pearson said:
    That must be an error.

    This is a background for the change:

    Above is a clip from BS 7671:2018+A2:2022. NOTE 1 is intending to tell us that there are two conditions where the minimum value of RA ev should be taken as 200 Ω:

    (a) Where the formula preceding the NOTE leads to a value of resistance exceeding 200 Ω; and
    (b) Where the formula preceding the NOTE gives a negative or invalid (division by zero) value of resistance.

    The formula will give a negative value of resistance where ImU0Cmax ≤ 70 (IL1+IL2+IL3), i.e. for very small neutral currents. Rearranging this inequality, we get:

    Which is clearly not was was printed in BS 7671:2018+A2:2022, and hence there was in error here (as above).

    AJJewsbury said:
    Most worrying there seem to be some small but significant changes (e.g. > changing to ≤ in A722,3) which aren't indicated at all (in that case I suspect it's just a correction of an earlier error, but it's still a change from the previous published version as far as I can see).

    Yes, I can see this in my printed version, and the version on VitalSource that's not EPUB 3 format.

  • 0 in reply to AJJewsbury
    AJJewsbury said:
    Many show only stylistic differences (e.g. "r.m.s." changes to "RMS") while others seem to appear where I can see no changes at all.

    Style changes (such as moving to all caps, or changing list formats) have not changed the actual of the requirement, and therefore were not considered a 'change' - it's just formatting.

  • 0 in reply to gkenyon

    Graham, thank you - that is v. helpful.

    gkenyon said:
    minimum value of RA ev should be taken as 200 Ω

    Surely that is maximum, not minimum? i.e. even if the equation allows RA ev to be > 200 Ω, it should never be greater than this value.

    gkenyon said:
    The formula will give a negative value of resistance where ImU0Cmax ≤ 70 (IL1+IL2+IL3)

    Or ∞ when ImU0Cmax = 70 (IL1+IL2+IL3). That was what was bothering me.

    Looking back to the blue book, it explained in the note to A722.3 that where the equation was invalid, condition (i) in 722.411.4.1 applied, but that was deleted in the brown book.

  • 0 in reply to Chris Pearson
    Chris Pearson said:
    Surely that is maximum, not minimum?

    Yes, sorry ... 

  • 0 in reply to Chris Pearson
    Chris Pearson said:
    Looking back to the blue book, it explained in the note to A722.3 that where the equation was invalid, condition (i) in 722.411.4.1 applied, but that was deleted in the brown book.

    Below is NOTE 1 to A722.3 from Amendment 1:2020 to BS 7671:2018 (with my highlighting):

    The reason NOTE 1 was changed in BS 7671:2018+A2:2022, is that 722.411.4.1 (i) was deleted.

    Therefore, the 'phase balance' option not being available to you, the earth electrode would have to remain ... although its value should not exceed 200 Ω as the note to Table 41.5 tells us values above this might not be stable. Hence, NOTE 1 was re-written for BS 7671:2018+A2:2022, but, having a different 'sense', the sign in the inequality was not amended correctly ... leading to the error discussed above.

    Hope that makes sense ... it was a change necessary as a consequence of changing something else, if you will.

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  • 0 in reply to Chris Pearson
    Chris Pearson said:
    Looking back to the blue book, it explained in the note to A722.3 that where the equation was invalid, condition (i) in 722.411.4.1 applied, but that was deleted in the brown book.

    Below is NOTE 1 to A722.3 from Amendment 1:2020 to BS 7671:2018 (with my highlighting):

    The reason NOTE 1 was changed in BS 7671:2018+A2:2022, is that 722.411.4.1 (i) was deleted.

    Therefore, the 'phase balance' option not being available to you, the earth electrode would have to remain ... although its value should not exceed 200 Ω as the note to Table 41.5 tells us values above this might not be stable. Hence, NOTE 1 was re-written for BS 7671:2018+A2:2022, but, having a different 'sense', the sign in the inequality was not amended correctly ... leading to the error discussed above.

    Hope that makes sense ... it was a change necessary as a consequence of changing something else, if you will.

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