What it is and what it does
The Siemens 5SM3352-6 is a 4-pole residual current circuit breaker (RCCB) from the SENTRON 5SM3 series, designed for 50 Hz systems. It carries a 25 A rated current at 500 V AC and a 10 kA short-circuit current rating, so it safely interrupts fault currents up to that level without cascading damage upstream in the distribution board. This is a Type A RCCB — it detects sinusoidal AC residual currents plus pulsating DC residual currents, which covers modern loads with half-wave rectification (switched-mode power supplies, variable-speed drives, LED drivers). The instantaneous design means no intentional time delay; it trips within the natural response time of the sensing coil.
Mounting and panel integration
Snaps onto a DIN rail (REG profile) and occupies 4 width units (36 mm wide, 90 mm tall, 70 mm deep). Mounting position is unrestricted — any orientation works. The supply can enter from top or bottom, which simplifies busbar routing in a crowded enclosure. IP20 with conductors connected; suitable for enclosed distribution boards only, not for wet or dusty environments.
Thermal derating and operating range
The 25 A rating holds at 40 °C and 45 °C. Above that, derate linearly: 24 A at 50 °C, 23 A at 55 °C, 22 A at 60 °C, 21 A at 65 °C, 20 A at 70 °C. Ambient operating range is -25 °C to 45 °C (maximum 75 °C, minimum -40 °C for storage). If the panel ambient runs hot — say, a sealed enclosure with drives — factor the derating into the load calculation.