Bussmann SC-20 20 Amp Time-Delay Class G Melamine Tube, 600V UL Listed Compact branch-circuit unit with high interrupting rating and current-limitation With 600V rating, it can be used in 120/208, 120/240 and 277/480V circuits Length variations relative to case size make this a "rejection" type fuse In general, SC fuses are about 1/3 the size of the 600V NEC fuse type Fuse has a degree of overload time-delay which permits it to pass temporary overloads. At 200% load, it has a minimum opening time of 12 seconds