Comment by aix1
5 hours ago
This sounded surprising and so I picked the first fuse I could find on RS and looked at its datasheet [1].
The characteristic curve shows that the 10A fuse is expected to blow after about 4s at 20A. Of course there's sample-to-sample variation and different ambient conditions etc, but how do those four seconds become "an hour to blow or not blow at all"?
Fuses can vary a lot -- even amongst examples with the same ratings, from the same box (and presumably, the same production batch).
Dave Jones of EEVBlog fame did some experiments with this several years ago: https://www.youtube.com/watch?v=WG11rVcMOnY
(I'm not arguing for or against any concept here; I'm just presenting some non-datasheet data.)