The Siemens SENTRON 5SU1354-1LB10 is a combined residual current circuit breaker with integral overcurrent protection — an RCBO — in a 2-module-wide (36 mm) package that snaps onto standard DIN rail. It carries a 10 A rated current at 30 °C with a C tripping characteristic (magnetic release between 5× and 10× In), and its residual-current element is type AC, meaning it detects sinusoidal AC fault currents only. The unit is 1P+N, switching the line conductor while the neutral is switched through but not protected against overcurrent. Breaking capacity is rated at 10 kA per EN 60898 and 20 kA per IEC 60947-2, which gives the 5SU1354-1LB10 headroom for installation at the origin of a sub-distribution board where fault currents can exceed the lower standard. The design is listed as short-time delayed G and super resistant K, which means the residual-current element tolerates brief surge currents (from lightning or capacitor switching) without nuisance tripping, and the overcurrent element handles higher inrush without degrading — provided the prospective short-circuit current stays within the 20 kA IEC rating.
Thermal derating and mounting
The 10 A rating holds at 30 °C ambient. At 40 °C it derates to 9.5 A, at 50 °C to 9 A, and at 60 °C to 8.5 A. By 70 °C the continuous current is 7.7 A. This matters in a sealed enclosure or a crowded DIN rail where internal temperature rise is unavoidable — the designer must either load the circuit below the derated figure or ventilate the panel to keep ambient under 40 °C. Mounting position is unrestricted, which simplifies layout in a vertical or horizontal busbar system. The 5SU1354-1LB10 occupies 2 modular width units (36 mm) on the DIN rail, with an installation depth of 70 mm and overall depth of 77 mm. Supply can enter from top or bottom, which avoids re-routing when the RCBO replaces an existing unit in a wired panel. The IP20 rating applies only when the distribution board is installed with connected conductors — that is, it is not a standalone weatherproof device, so it belongs inside a rated enclosure.