The Siemens SENTRON 5SU1354-0LB20 is a 2-pole RCBO (residual current circuit breaker with overcurrent protection) in a 1P+N configuration, rated for 20 A with a B tripping characteristic. It breaks fault currents up to 10 kA per EN 60898, which means it's sized for standard residential and light commercial distribution boards where the prospective short-circuit current stays under that threshold. The 36 mm width (2 width units) and 70 mm installation depth let it slot into a SENTRON distribution board without forcing a wider enclosure.
Thermal derating and conductor sizing
The 20 A rating holds at 30 °C ambient. At 40 °C it derates to 18.8 A, at 50 °C to 17.4 A, and at 55 °C to 16.2 A — the upper end of its operating ambient range. If the panel runs warm, size the downstream load for the derated figure, not the nameplate. Both solid and stranded conductors from 0.75 mm² up to 35 mm² are accepted, which covers everything from lighting circuits to submain feeds. Maximum power dissipation is 7.4 W, so thermal buildup in a tightly packed enclosure is manageable.
Mounting and environment
Mounts in any position — no derating needed for horizontal or inverted orientation. IP20 when installed in a distribution board with conductors connected; that's the standard for enclosed panel gear, not for open wet areas. Overvoltage category III means it's rated for fixed installation downstream of the main distribution board. The supply can enter from either top or bottom, which saves a rewire if the panel layout changes. Halogen-free and silicon-free construction matters for environments where outgassing during a fault could damage nearby electronics or contaminate clean processes.