Siemens SENTRON 5SM1342-6KK01 is a 4-pole residual current circuit breaker (RCCB) rated 25 A at 40 °C, with a 30 mA trip threshold and Type A fault-current detection. It is short-time delayed, meaning it rides through brief inrush events without nuisance tripping — useful on circuits with capacitive or surge loads. Mounts on DIN rail (REG) and fits any orientation. The screw terminals accept solid or stranded copper from 1.5 mm² up to 25 mm², with a tightening torque of 2.5 to 3 N·m. That's a wide wire range — covers everything from a 1.5 mm² lighting circuit tail to a 25 mm² subfeed. Installation depth is 55 mm, and it occupies 4 width units (about 72 mm) on the rail.
The 25 A rating holds up to 45 °C ambient. Above that, derate linearly: 24 A at 50 °C, 23 A at 55 °C, 22 A at 60 °C, 21 A at 65 °C, and 20 A at 70 °C. The storage range is -40 to +60 °C, which is wider than the operating range; that limit governs handling, not running.