UK MCB's vs Cartridge fuses

[clanky]

Hi all, need to pick the collective brains as im concerned about a recent problem. We have a few freezers here on our small holding and one of them started playing silly buggers. Eventually the 20A MCB kept tripping so to make sure it was the freezer i put it on a different circuit with a 16A breaker and the same thing happened. When i pulled the freezer out, i was met with a massive mouse nest in the drip tray above the motor and the flex wire had been proper nibbled at. So quick clean up, new flex plus some mouse traps and all was cured. The problem is i dont understand why the 13A fuse in the plug didnt blow and why was a 13A fitted anyway when the original flex cored was 0.75mm2, which according to the tables, is only good for 6A. As i live in a wooden barn conversion, it scares the heeby jeebies out of me when i see things like this. Anybody shed any light on this?

 

[R-fur]

Its important to remember that a plug top fuse is just a rewireable fuse that's convenient to change and shouldn't be confused with a HRC fuse.
When I started out with this nonsense in the 70's the 14th edition was in vouge, protective devices were classed as course or close. The definition of close protection was that at twice the rated current it would operate within four hours! Plug top fuses are course protection.