The selective design means it coordinates with downstream RCCBs — it holds through short-duration earth faults to let the downstream device clear first, which keeps upstream circuits live on a faulted branch. Mounts on DIN rail (REG), occupies 4 width units (72 mm), and accepts conductors from 1.5 to 25 mm² solid or stranded. The N-left variant positions the neutral on the left side of the device.
Selective (time-delayed) RCCBs are the backbone of graded earth-fault protection in distribution boards. The 5SM3646-8KL is designed to delay its trip long enough for a downstream non-selective RCCB to clear a fault first — typically up to several hundred milliseconds. This avoids a full-panel blackout when a single branch faults. If your installation has three-phase rectifiers or single-phase electronics, Type A is the minimum required by IEC 60364. The 300 mA tripping threshold is typical for fire protection or sub-distribution where nuisance tripping from leakage currents must be avoided — it is not for direct personal shock protection (30 mA is the standard for that).
Tightening torque is 2.5 to 3 N·m. Overvoltage category III. Finger and back-of-hand safe per the protection against electrical shock classification. Silicon-free construction.