The Siemens 5SM1344-0 is a SENTRON residual current operated circuit breaker (RCCB) — 4-pole, type AC, rated 40 A with a 30 mA trip threshold at 400 VAC.
The 40 A rating holds at 40 °C and 45 °C ambient; above that the unit derates linearly — 38.4 A at 50 °C, 36.8 A at 55 °C, 35.2 A at 60 °C, 33.6 A at 65 °C, and 32 A at 70 °C. The 10 kA short-circuit current rating (SCCR) covers most building-level fault currents; the I²t let-through is 70 000 A²·s, and the let-through current peaks at 7 500 A — both figures an upstream MCB needs to coordinate with. Installation depth is 55 mm. For circuits with variable-speed drives, LED lighting, or other electronics that can generate DC fault components, a type A or type B RCCB would be required. This unit is silicon-free, which matters for potting and coating compatibility in some industrial panels.