On Wednesday, 3 January 2018 10:37:47 UTC, Harry Bloomfield wrote:
tabbypurr expressed precisely :
On Tuesday, 2 January 2018 23:10:04 UTC, wrote:

I need to replace an ancient bell/call box power supply with a modern
wallwart. The original transformer (from the 1930s, with internal fuses
in both L and N) was wired into the lighting circuit. It would be very
difficult to get non-lighting power to this location (near the ceiling,
in the kitchen), I don't have space for a fused spur and I can't find a
13A socket with a built-in fuse. I'm planning on using a standard 13A
socket, fitting an internal 500mA in-line fuse and adding a suitable
label to the socket.
What does the jury think?

won't be a problem. But any mains fuse below 3A does fail in time.


NT

Fuses range in value from ratings of 1,000's of amps, down to just a
few milliamps in equipment fuses. They only tend to blow when subjected
to either a fault load or a regular surge load.

by definition they don't 'blow' when they break, they just break.