Type S/Adapter Fuses

Type S/Adapter Fuse Graphic Type S fuses are also called tamper proof fuses because each fuse size has a different base and thread size. These fuses also require the use of a special adapter which is screwed into the standard Edison base of the fuse holder. The adapter has a standard Edison base thread on the outside but a special sized diameter and thread on the inside. It also has a spring barb on the outside that projects into the standard Edison base shell of the fuse holder and prevents the removal of the adapter once it has been installed. The different sized base and thread size is such that a larger size S base fuse cannot be screwed into the adapter. The adapters have amperage ratings the same as the fuses which go in them. If a 20 amp adapter is installed in a fuse holder, it is impossible to use an S type fuse higher than a 20 amp rating in the adapter.