Learned something about fuses today

[Skyfox]

I have to say, finding certain specifics about fuses and other components can be a real pain sometimes!

Yesterday I found a ceramic tube fuse that turned out to still be good, so I figured I'd look up the specs on it to know what it is.  Here's the info on the end cap (as I first read it and searched for it):
side:  H250VF3.15A
end:  Littlefuse logo and Semko mark
(the end of the other cap has the BSI [British Standards Institute] kitemark, and the side is blank)

Since the A ran right into the H I thought maybe the part number started with AH.  In reality, I was confusing myself because when I did the part search I duplicated it by looking for AH250V3.15A, and of course very little came up, and then I realized the error and searched without the extra A.  But 3.15 amps seemed a bit obscure, so I thought it was a 15 amp fuse and F3 was some kind of product code.

I looked up the Littelfuse datasheets and fuse catalog, eventually finding ceramic fuses of this size, in the Littelfuse series 215 (slow-blow) and 216 (fast blow).  My guess was that the F may mean fast, but neither datasheet describes how to decode the markings on the side of the fuse cap.  They listed how to read the part number when you order a reel of fuses or something.  It was the same when looking up these fuses in Digikey or Mouser because neither site showed that specific string of characters on the part pages and the datasheet links referred right back to the ones I already read.

I finally had a break when I noticed there was a slight misalignment between the V and F.  So I did a search for F3.15AH250V, and there it was!  I learned that the letters and numbers on the side of the fuse are called the IEC markings (International Electrotechnical Commission).  What came up brought me to the specific page on Littelfuse's page for this exact fuse which listed that IEC marking exactly as it shows up on the cap.  Turns out, the F does in fact mean fast blow, while it it was a slow-blow it would be a T for timed blow.  If I'd read the catalog more thoroughly it would have told me about that.  And the H stands for high breaking capacity.  They should include the IEC marking in the datasheet.

And it only took 45 minutes!