The Siemens 5SM3342-0KL is a 4-pole residual current circuit breaker (RCCB) from the SENTRON 5SM3 series, type AC, rated 25 A at 30 mA sensitivity and 400 V AC. The 30 mA trip threshold means it provides supplementary protection against direct contact — the level required for general socket-outlet circuits and wet areas in most IEC-based installations. It is an instantaneous design (no intentional time delay), so it trips within a cycle on a residual fault — fine for circuits where nuisance tripping from transient leakage is not expected.
Snaps onto DIN rail (REG profile), occupies 4 width units (about 72 mm), and accepts conductors from 1.5 mm² up to 25 mm² solid or stranded. Terminal torque spec is 2.5 to 3 N·m — a mid-range value that works with standard screwdriver bits; over-torquing past 3 N·m can strip the terminal.
The IP20 protection class applies only when the distribution board is installed and conductors are connected — the terminals are finger-safe but not sealed against dust ingress during handling. Silicon-free construction is noted, which matters for potting or conformal-coating processes where silicone outgassing can cause adhesion failures.