Type S plug fuses must be used together with a matching Type S adapter that screws into the Edison-base fuse holder (fuse socket). The adapter is required so the Type S plug fuse can be installed and so the circuit cannot be overfused.

Quick Scoop

  • Type S plug fuses are designed to work only in special Type S adapters installed in standard Edison-base fuse holders.
  • The adapter is sized for the correct ampere range and prevents someone from screwing in an oversized fuse that could overheat the wiring.
  • Electrical codes require that Edison-base fuseholders be converted with Type S adapters if Type S plug fuses are used, specifically to stop tampering and overfusing in older fuse panels.

In simple terms: when Type S plug fuses go into a fuse holder, a non- removable Type S adapter must be installed in that holder so only the proper size Type S fuse will fit.

TL;DR: The device that must be used in conjunction with Type S plug fuses in a fuse holder is a Type S fuse adapter (Type S adapter ring) that screws into the fuse holder and permanently converts it for Type S fuses.

Information gathered from public forums or data available on the internet and portrayed here.