The Siemens SENTRON 5SM3646-6KL is a 4-pole residual current circuit breaker (RCCB) rated for 63 A at 400 V AC, with a 300 mA type AC tripping characteristic. It's an instantaneous device — no intentional delay — so it trips as soon as the residual current exceeds the threshold. That makes it a fit for general-purpose earth-leakage protection where nuisance tripping from transient surges isn't a concern.
Snaps onto DIN rail (REG) and occupies 4 width units at 72 mm wide. The neutral is wired on the left side (N left variant). Mounting position is any, so vertical or horizontal busbar arrangements work. IP20 protection applies once the distribution board is installed and conductors are connected; the device itself isn't rated for wet environments.
What the ratings mean
The 300 mA residual threshold is higher than the 30 mA used for personal shock protection — it's typically specified for fire prevention or equipment protection where some leakage is expected. Type AC means it detects sinusoidal AC residual currents only; pulsating DC or smooth DC faults won't trip it, so don't use it downstream of variable-speed drives or UPS systems without verifying the fault-current profile. Surge current resistance is rated at 1 kA, which means it can withstand the inrush from a nearby lightning strike or switching surge without welding the contacts or false-tripping. Mechanical life is 10,000 switching cycles typical — adequate for a protective device that operates infrequently, not a switching contactor.
Ambient limits and approvals
Overvoltage category III, so it's suitable for fixed installation downstream of the utility meter. Finger and back-of-hand safe per the shock-protection design. Silicon-free construction — relevant for potting or conformal-coating processes in sensitive electronics environments.