Siemens SENTRON 5SU1354-6LB40 — RCBO, B-Curve 40 A, Type A
The Siemens SENTRON 5SU1354-6LB40 is a 2-pole (1P+N) residual current circuit breaker with overcurrent protection (RCBO) rated 40 A at 30 °C with a B-curve tripping characteristic. It combines a Type A residual current device (sensitive to pulsating DC and AC sinusoidal residual currents) with a thermal-magnetic overcurrent trip in a single 2-module-width (36 mm) package that snaps onto DIN rail. Breaking capacity is 10 kA per EN 60898 and 15 kA per IEC 60947-2 — the IEC 60947-2 figure is the one to use for industrial panel coordination where higher fault current is expected. The short-time delayed G characteristic and super resistant K design mean this unit tolerates brief inrush without nuisance tripping, which matters on circuits feeding small motor loads or capacitive power supplies.
Thermal derating and panel integration
At 40 °C ambient the rated current drops to 37.6 A; at 50 °C it is 34.8 A; at 70 °C it is 29.2 A. If the panel runs hot — say a packed enclosure with multiple breakers — use the 40 °C or 50 °C column for the actual load limit. The 77 mm depth (70 mm installation depth) fits standard distribution boards; the supply can enter from either top or bottom, which simplifies busbar routing. Rated IP20 with conductors connected and the distribution board installed — this is a panel-internal device, not for wet or outdoor locations. Halogen-free and silicon-free construction matters for environments where outgassing during a fault could damage nearby electronics or contaminate clean-room processes.