The Siemens SENTRON 5SL6120-6BB is a 1-pole miniature circuit breaker rated 20 A with a B-curve tripping characteristic, designed for protecting final circuits in residential buildings and infrastructure installations. It breaks fault currents up to 6 kA per EN 60898 and IEC 60947-2, which covers the typical prospective short-circuit current at the service entrance of most residential and light commercial panels. The 18 mm width (one modular unit) drops into any standard DIN-rail enclosure without needing to shuffle adjacent breakers — a straight swap for a failed or undersized 20 A B-curve unit.
The B-curve means the magnetic trip activates at 3 to 5 times rated current (60–100 A for this 20 A unit), making it suitable for resistive and lighting loads with modest inrush — think general-purpose sockets, lighting circuits, and small appliances. The 6 kA breaking capacity is the maximum fault current the breaker can safely interrupt at its rated voltage; at 400 V AC this is adequate for most residential and light commercial service entrances, but verify against the available fault current at the point of installation — if your panel's SCCR exceeds 6 kA, you need a higher-rated upstream device or a current-limiting breaker.
Panel Integration — DIN Rail and Wiring Notes
The 18 mm width occupies one modular unit, and the 70 mm installation depth leaves clearance behind a standard 80 mm deep enclosure. Spring-cage terminals accept 0.2–2.5 mm² solid or ferruled stranded wire; strip length is 8 mm. The breaker is sealable for tamper-proof applications, and the halogen-free, silicon-free construction suits installations where outgassing during a fault must be minimized.