Although HRC fuses have an excellent ability to interrupt fault currents of high
value, they can experience difficulty in interrupting overcurrents of low value. Fault
currents of about three times the normal current rating of the fuse can be at the level
where some difficulty in clearing the fault may occur. This difficulty is because at such
low levels of current the fuse element pre-melting time can be up to several seconds,
or even minutes. This causes the fuse elements to heat up unequally so that instead
of the elements melting simultaneously at all of their series notches, only one or two
breaks may occur at the hottest spots