safety - Maximum fuse rating before a MOV (varistor)

I just watched some scary videos of MOV's catching fire and I've flee'd here to ask you guys for help.

I understand that it's a good idea to put a fuse in front of a MOV, considering it fails short-circuit. However, is there a maximum fuse size that can be used before the MOV?

I'm pondering the possibility of a MOV failing partially short-circuit which then runs away to become a fire hazard. i.e. the short might be enough to blow a 1A fuse but not enough to blow a 13A fuse.

• Would it be safe to rely on a varistor to blow a standard, household 13A fuse found in a mains plug?


• Would it permit too much power?