The Siemens SENTRON 5SM6021-1 is an arc-fault detection unit block — an AFDD — designed to detect and interrupt dangerous series and parallel arcs in final circuits. This is the detection block itself, intended for use with a compatible MCB (5SY or 5SL4 series) or RCBO (5SU1 series) to form a complete arc-fault protective device.
The 5SM6021-1 distinguishes between series arcs (an arc in the load circuit, e.g., a loose terminal or damaged cable) and parallel arcs (an arc line-to-neutral or line-to-ground). For series arcs, it detects and clears faults from 1 A up to 20 A. For parallel arcs, the detection range is 50 A to 500 A. The 1 A minimum series-arc threshold is critical: it catches low-energy arcing that a standard MCB might not trip on, which is the whole point of an AFDD. The 500 A parallel-arc ceiling covers high-energy faults up to the short-circuit capacity of the upstream breaker.
The unit occupies 1 width unit (18 mm) on DIN rail, with a total width of 54 mm including the adjacent protective device it mounts to. Depth is 68.5 mm, height 95 mm, and installation depth 70 mm — standard for SENTRON modular devices. Mounting position is any orientation. The IP20 rating applies with the protective device and conductors connected, which is typical for enclosed distribution boards. The 2-pole (1P+N) design switches the line and switches or isolates the neutral.