The Siemens 5SM3312-6KL01 is a SENTRON 5SM3-series residual current circuit breaker (RCCB), 2-pole, Type A, short-time delayed, rated at 25 A with a 30 mA trip sensitivity at 230 V AC. This is the N-left variant, meaning the neutral conductor connects on the left side of the device — a detail that matters when laying out the DIN-rail assembly in a distribution board so the busbar or wiring aligns correctly.
The Type A designation means it detects pulsating DC residual currents as well as sinusoidal AC, so it covers modern loads like rectifiers, switched-mode power supplies, and variable-speed drives that generate pulsed DC fault currents; a plain Type AC device would miss those. The short-time delayed characteristic (also called selective or S-type) introduces a deliberate delay before tripping, allowing downstream RCCBs to clear first — this is how you achieve selectivity in a multi-level distribution panel so a fault on a sub-circuit doesn't take out the entire board. Rated at 25 A continuous, this RCCB is sized for a branch circuit feeding a group of outlets or a small sub-panel, not a single high-draw appliance. The 3 kA surge current resistance (rated impulse withstand) means it can tolerate the inrush from nearby lightning or switching transients without nuisance tripping — a real concern in industrial environments with frequent contactor or motor switching.
Terminal capacity accepts 1 … 16 mm² solid or stranded copper; tighten to 2.5 … 3 N·m. The screw-type terminals are finger and back-of-hand safe (IP20 once installed in the distribution board with conductors connected). Ambient operating range is -25 … +45 °C, storage from -40 … +75 °C.