The Siemens SENTRON 5SM3646-8 is a 4-pole residual current circuit breaker (RCCB) rated 63 A at 40 °C, 400 V AC, 50 Hz. The selective design (time-delayed) means it coordinates with downstream RCCBs: on a fault, the downstream unit trips first, keeping upstream circuits live — critical for a distribution board feeding multiple sub-panels or machine cells where you want nuisance trips isolated to the faulted branch.
Rated 63 A at 40 °C and 63 A at 45 °C — no derating needed in a typical 40 °C panel ambient. At 50 °C it derates to 60.48 A, at 60 °C to 55.44 A, and at 70 °C to 50.4 A. If your panel runs hot, size the upstream breaker accordingly. The I²t let-through is 70 000 A²·s, and the permissible let-through current is 7 500 kA — these matter for coordination with the upstream MCB or fuse. Mounts on DIN rail (REG), occupies 4 width units — 72 mm wide, 90 mm tall, 77 mm deep, with an installation depth of 70 mm. Finger and back-of-hand safe per IP20 once the distribution board is installed and conductors connected.