The Siemens 5SM3312-3 is a 2-pole SENTRON residual current circuit breaker (RCCB) rated 25 A at 230 V AC, with a 30 mA trip threshold and Type F fault-current discrimination. It is short-time delayed, meaning it withstands brief surge currents up to 3 kA without nuisance tripping — useful on circuits feeding switched-mode power supplies or drives that produce mixed-frequency leakage.
Rating and derating across ambient temperature
Full rated current of 25 A is maintained up to 45 °C ambient. Above that, derating applies: 23.5 A at 50 °C, 22 A at 55 °C, 20.5 A at 60 °C, 19 A at 65 °C, and 17.5 A at 70 °C. The maximum permissible ambient is 75 °C; minimum is -40 °C.
Type F fault current and short-time delay
The short-time delayed switching function (3 kA surge current resistance) prevents false trips from transient surges — common on motor-start or capacitor-switching events. Rated short-circuit current is 10 kA.
Installation depth is 70 mm. Mounting position is any orientation. IP20 protection with connected conductors in a distribution board. Finger and back-of-hand safe per the shock protection class.