What this SENTRON RCCB does on the line
The Siemens 5SM3612-0KL is a 2-pole residual current circuit breaker (RCCB) from the SENTRON 5SM3 family, rated 25 A at 230 V AC with a 300 mA tripping residual current. The 300 mA threshold is a ground-fault protection level, not a personnel-safety trip (those are 30 mA or lower); it guards against insulation degradation and fire risk on distribution subfeeds or equipment circuits. Mounts on DIN rail (REG) and occupies 2 width units. Installation depth is 70 mm. The N terminal is on the left side of the device (N left variant). Finger- and back-of-hand safe per the touch-protection rating, so it meets the basic IPXXB requirement for live-part guarding inside an enclosed distribution board.
Terminal capacity and wiring constraints
That 16 mm² upper end is generous for a 25 A device — it lets you land a feeder tail oversized for voltage drop or parallel supply without a reducer. The IP20 rating applies only when the distribution board is installed and conductors are connected; the device itself is not sealed for wet environments.
Operating ambient temperature range is -5... +45 °C; storage range is wider at -40... +75 °C. The device is instantaneous-trip (no intentional short-time delay) and silicon-free.