Selective RCCB for 400 V AC feeder protection
The Siemens 5SM3446-8 is a 4-pole selective RCCB from the SENTRON series, rated at 40 A at both 40 °C and 45 °C ambient, with a 100 mA residual tripping current and Type A waveform sensitivity. Selective design means it introduces a deliberate time delay so that downstream RCCBs trip first, keeping this unit as the backup — critical for feeder coordination in a distribution board where you want the branch, not the main, to clear a ground fault.
Thermal derating and SCCR headroom
Rated 40 A up to 45 °C, then derates linearly to 28 A at 70 °C — a 30 % drop. Short-circuit current rating is 10 kA per IEC 61008-1, with an additional 0.8 kA rating under EN 60898. The 10 kA figure governs the upstream breaker coordination; the 0.8 kA is a conditional rating for the RCCB's own breaking capacity under standard test conditions.
Mounts in any position.