I'm starting to get a bit annoyed about this new phenomenon of curtailment of discussions which, although protracted, are well mannered, 'of interest' and (at least in this case) at least partially related to the topic of a thread. Maybe it's time for me to take another rest from the forum!
As I said, the equivalent is not true of other fuses which do not necessarily satisfy 433.1.1(iii) even though they satisfy 433.1.1(ii).
Kind Regards, John
For the reasons I went on to explain...EFLImpudence said:Is it? Why?
I think you may be missing my point. In the case of a BS 3036, 433.1.202 supersedes 433.1.1(ii), but 433.1.1(iii) still also has to be satisfied (as you say, "and"). However, as I explained, given a 'fusing factor' of 2, if 433.1.202 is satisfied (by a 3036), then 433.1.1(iii) is automatically also satisfied - that's an arithmetical inevitability (for any 'fusing factor' above 1.45).EFLImpudence said:I do not see why. If 433.1.1(iii) is NOT satisfied then then (i) and (ii) are irrelevant. It must satisfy all three - 'and' not 'or'.
As I said, the equivalent is not true of other fuses which do not necessarily satisfy 433.1.1(iii) even though they satisfy 433.1.1(ii).
I think the real question is why they bothered to single out BS 3036s. Given the existence of 433.1.1(iii), I can't see that the situation (for 3036s) would be any different if 433.1.202 didn't exist, would it? Satisfaction of 433.1.1(iii) would effectively involve use of the 'de-rating factor' (which is implicit in the determination of I2) - and if (iii) were satisfied, then (ii) would be satisfied as well.EFLImpudence said:Why then are BS3036 fuses singled out as they are only 5% 'worse' than BS1362 fuses?
As explained above.EFLImpudence said:Why not?
Exactly - hence the 'F' in what I wrote. For a 3A cable, the In of the fuse would have to be no greater than 3A x (1.45/F).EFLImpudence said:For a 3A fuse and 3A cable, it isn't. Therefore the derating factor applies.
I don't doubt that it would be 'alright' (particularly given that the CCC of a non-flexible 0.5mm² cable {in free air} would {if we were allowed to use it} presumably be considerably more than 6A). However, I'm not sure how you could read BS7671 as saying that it was 'alright'!EFLImpudence said:They are, so perhaps 3A flex (0.5mm²) is alright with a 6A MCB
Kind Regards, John
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