20 A B-curve MCB for branch-circuit protection
The Siemens 5SJ6120-6 is a 1-pole miniature circuit breaker from the SENTRON 5SJ6 series, rated 20 A with a B tripping characteristic and a 6 kA breaking capacity per EN 60898 and IEC 60947-2. The B-curve trips between 3 and 5 times rated current — suited for resistive and general-purpose loads where inrush is modest, not for motor-starting circuits that need a C or D curve. The 6 kA interrupting rating means it can safely clear a fault up to that level on a 240 V AC or 60 V DC circuit; at 440 V AC (multi-phase operation) the maximum voltage is higher, but the SCCR stays at 6 kA. Single-pole format, 18 mm wide (one modular width), snaps onto DIN rail in any mounting position. The housing is IP20 with connected conductors — standard for enclosed distribution boards. Terminal capacity accepts solid or stranded conductors from 0.75 to 25 mm², which covers most branch-circuit wiring up to 20 A. Installation depth is 70 mm; overall depth including terminals is 76 mm.
Compliance and documentation
The 5SJ6 series carries IEC/EN 60898 and IEC 60947-2 ratings, with a 6 kA breaking capacity under both standards. Overvoltage category 3, pollution degree 2 (implied by IP20). The design is halogen-free and silicon-free, and the breaker is sealable for tamper-evident installations. Vibration resistance per IEC 60068-2-6: 50 m/s² at 25–150 Hz and 60 m/s² at 10–150 Hz. Mechanical service life is 20 000 switching cycles typical.