The Siemens 5SM1342-6KK03 is a 4-pole residual current circuit breaker (RCCB) from the SENTRON 5SM1 series, type A, rated at 25 A and 30 mA residual tripping current on a 400 V AC supply. Rated short-circuit capacity is 10 kA.
Occupies 4 width units (72 mm at 18 mm per unit). Installation depth is 55 mm — fits shallow enclosures where a deeper device would hit the gland plate. Mounts in any orientation. Supply can land on top or bottom terminals — no polarity constraint on the line/load side for this RCCB. Finger and back-of-hand safe terminals (IP20 with conductors connected) meet the basic shock-protection requirement for distribution boards. Silicon-free construction matters if this panel shares air with potting, coating, or conformal-coating processes — no silicone outgassing to contaminate bond pads or optical surfaces.
Rated 25 A at both 40 °C and 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, 20 A at 70 °C. If the enclosure runs hot — say 55 °C inside a sealed cabinet — plan for 23 A continuous, not the nameplate 25. Storage range extends to -40 °C to 60 °C — the wider storage limit covers shipping and warehouse, not running conditions.