The Siemens SENTRON 5SM1312-0 is a 2-pole residual current circuit breaker (RCCB) rated for 25 A at 40 °C with a 30 mA trip threshold, Type AC waveform detection. It's the kind of part you spec into a distribution board when you need basic earth-leakage protection on a single-phase 230 V AC circuit — no delayed switching, no DC-sensitive electronics inside, just a straight instantaneous trip on sinusoidal AC fault currents. The 10 kA short-circuit current rating (SCCR) means it can handle a hard fault upstream without welding its own contacts shut.
Temperature derating and mounting
Rated current holds at 25 A up to 45 °C ambient, then derates linearly — 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. Mounting is DIN rail (REG), any orientation, with top or bottom feed — no need to rework the busbar layout when swapping an older unit. The 55 mm installation depth fits standard 2-module-width enclosures.
Coordination and compliance
Back-up protection: the RCCB is rated for 0.5 kA withstand per EN 60898 and IEC 61008-1, so it needs an upstream MCB or fuse rated at or below that to clear a fault without damaging the RCCB. The I²t let-through is 70 000 A²·s; the let-through current peaks at 7 500 A. Overvoltage category III — suitable for fixed-installation distribution boards. IP20 with conductors connected, finger and back-of-hand touch-safe. Silicon-free construction, which matters if the panel shares space with potting or conformal-coating processes.