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.
What the ratings mean for fit
The 30 mA rated residual current is the standard for personal protection against direct contact in residential and commercial circuits — it trips when leakage exceeds that threshold, which is low enough to prevent ventricular fibrillation under most conditions. 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.
Panel integration and wiring
Snaps onto DIN rail (REG), occupies 2 width units (36 mm wide), and the 70 mm installation depth fits standard distribution board enclosures. 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.