The Siemens 5SU1354-1LB20 is a SENTRON RCBO (residual current circuit breaker with overcurrent protection) in a 2-pole 1P+N configuration, rated 20 A with a C tripping characteristic and 30 mA AC residual current sensitivity. It carries a 10 kA breaking capacity per EN 60898 and 20 kA per IEC 60947-2, so it can handle fault currents up to those levels without upstream coordination issues in most residential or light commercial distribution boards.
What the ratings mean for fit
The C-curve means the magnetic trip fires at 5–10× In, so it's suited for inductive loads like small motors or fluorescent lighting banks where inrush could nuisance-trip a B-curve. The 30 mA AC residual current type catches sinusoidal earth faults only — not pulsating DC or smooth DC, so it's correct for general-purpose circuits but not for variable-speed drives or EV chargers that generate DC fault content. Rated current derates with ambient temperature: 20 A at 30 °C, 18.8 A at 40 °C, 14.6 A at 70 °C. In a crowded enclosure running warm, the actual continuous load should be sized against the derated figure, not the 20 A label. The short-time delayed G and super resistant K design means this RCBO tolerates brief surge currents (e.g., from capacitor switching or transformer inrush) without nuisance tripping, while still clearing genuine faults. That matters in industrial panels where equipment start-up transients are routine.
Mounting and integration
Two modular width units at 36 mm wide, 90 mm tall, 77 mm deep, with 70 mm installation depth. Snaps onto DIN rail in any orientation. Supply can enter from top or bottom. IP20 with conductors connected and distribution board installed — standard for enclosed panel use, not for wet or outdoor locations.