What it is and what it does
The Siemens 5SU1644-1RC63 is a 4-pole RCBO (residual current operated circuit breaker with integral overcurrent protection) from the SENTRON family, rated 63 A with a C tripping characteristic and 300 mA AC type residual current detection. It combines overcurrent and earth leakage protection in one 7-module-wide unit, saving a DIN rail position compared to separate MCB+RCD assemblies. Rated breaking capacity is 10 kA per EN 60898 and 15 kA per IEC 60947-2 at 415 V AC, which covers most commercial and light industrial panelboard applications where the prospective short-circuit current stays under those thresholds. The C-curve trips between 5 and 10 times rated current, making it suitable for circuits with moderate inrush — motorized loads, banks of LED drivers, or small transformers where a B-curve would nuisance-trip but a D-curve would provide too little protection against arcing faults.
Panel fit and installation
Width is 126 mm (7 module units), depth 70 mm, height 90 mm. Mounts on DIN rail in any orientation. IP20 rating applies when installed in a distribution board with conductors connected — standard for enclosed panelboards, not for open or wet locations. Supply can enter from top or bottom. Rated insulation voltage (Ui) is 440 V, overvoltage category III, pollution degree 2 — typical for fixed-installation distribution boards in buildings and industrial switchgear. Operating temperature range -40 °C to +75 °C covers outdoor enclosures in cold climates and hot machine cabinets. Humidity tolerance up to 95%.