The Siemens SENTRON 5SM3446-8LA is a 4-pole residual current operated circuit breaker (RCCB) rated 63 A at 400 V AC, with a 100 mA trip threshold and Type A fault current sensitivity. The 100 mA rating means it's selective — it will not trip on a ground fault that a downstream 30 mA RCCB should clear, so only the faulted branch is isolated and the rest of the distribution board stays live. It includes thermal overload protection, so it also guards against sustained overcurrents, not just leakage — a feature that saves an extra protective device in the same DIN-rail slot.
Mounting position is any — vertical, horizontal, upside-down — no derating needed for orientation. Terminals accept solid or stranded conductors from 1.5 to 25 mm²; tighten to 2.5–3 N·m. Overvoltage category III means it's rated for fixed-installation distribution level, not for downstream equipment.