SOO Fuses are dual-element time delay Type S fuses designed for motor and motor branch-circuit protection; also suitable for all general purpose circuits.
The National Electric Code now permits Edison-base fuses to be used only for replacements in existing installations, and then, only when there is no evidence of over-fusing or tampering.
All new Edison-based fuse holders must have Type S fuse adapters installed before they are placed in service.
Designed to prevent installation of wrong size fuses, Type S Adapters (SAO series) screw into Edison-base fuse holders so they may accept Type S fuses. Once installed the adapters cannot be removed.
To prevent shunting of open fuses or over-fusing, and to reduce nuisance fuse opening, it is recommended that SAO adapters with properly rated SLO or SOO series fuses be installed in all Edison-base fuse holders.