What this RCCB is and what it does
The Siemens 5SM3646-4KK14 is a SENTRON-series residual current circuit breaker (RCCB) designed for 4-pole, 63 A circuits with a 300 mA Type B+ residual-current trip. The Type B+ classification means it detects smooth DC residual currents and high-frequency AC components — not just standard AC and pulsating DC — making it suitable for circuits with variable-speed drives, UPS systems, or EV charging equipment where non-sinusoidal fault currents are common. The 10 kA short-circuit current rating (SCCR) per IEC 61008-1 tells you it can safely interrupt a fault up to that level without welding contacts or cascading upstream.
Mounting and panel fit
Snaps onto a DIN rail (REG profile per) and occupies 4 modular-width units (72 mm wide, 77 mm deep, 90 mm tall). Mounting position is any orientation, and the installation depth behind the panel face is 70 mm. The IP20 rating applies when the distribution board is installed with conductors connected — standard for enclosed panelboards, not for open wet-area mounting.
Thermal derating and ambient limits
Rated 63 A continuously at 40 °C and 45 °C ambient. Above that, the device derates linearly: 60.5 A at 50 °C, 58 A at 55 °C, 55.4 A at 60 °C, 52.9 A at 65 °C, and 50.4 A at 70 °C. Operating ambient range is -25 °C to 45 °C; storage range extends from -40 °C to 75 °C. If your panel ambient runs above 45 °C, size the upstream breaker for the derated current, not the nameplate 63 A.