How Do Fuses and Fuse Boxes Work? - thespruce Fuses for standard circuits (not high-voltage appliance circuits) are called plug fuses and have screw-in bases. There are two different types of bases: the Edison base (found on Type T fuses) and the rejection base (found on Type S fuses). The Edison base (Type T) looks like a light bulb base and fits the standard sockets found in old fuse boxes.Author: Bob Formisano Scary Fuse Boxes | Old House Web If you find a fuse box stuffed with 30 amp fuses, or even all 20 amp fuses, chances are the fuses have been blowing frequently--and the occupants have installed heavier fuses than are safe. This house definitely needs additional wiring! Even if you find a newer 150 or 200-amp circuit breaker box, you're not entirely out of the woods.