S&C Electric Company 121200-R4 Refill Fuse Unit

The S&C Electric Company 121200R4 SM-4 Refill Fuse Unit is a 7.2 kV nominal, 8.3 kV maximum refill module rated at 125E (125 A), designed to drop directly into SM-4 and SML-4 fuse holders as a field‑replaceable element. This refill unit is part of S&C’s SM‑4 family and is also listed as suitable for SME‑4Z holders, enabling coordinated protection for indoor distribution feeders. With a 125 A ampere rating and a 7.2 kV nominal rating, it refills a blown fuse in three‑phase SM‑4 configurations without replacing the entire fuse assembly, supporting rapid system restoration after a fault. The 121200R4 variant specifically targets 7.2 kV systems; higher‑voltage variants in the same family, such as 122200R4 (14.4 kV nominal), exist for different installation needs.