What this RCBO is and what it does
The Siemens 5SU1354-3KK32 is a 2-pole (1P+N) residual current circuit breaker with overcurrent protection — an RCBO from the SENTRON 5SU1 series. It combines a 32 A thermal-magnetic B-curve MCB with a Type F residual current device in a single 36 mm wide (2 MW) module. Type F means it detects AC pulsating and smooth DC fault currents plus high-frequency residuals from variable-speed drives and LED lighting, which standard Type A devices miss. The 10 kA breaking capacity per EN 60898 covers most commercial and light industrial sub-distribution panels. Supply can land on either top or bottom terminals, and the unit mounts in any position inside an IP20 enclosure.
Thermal derating — the real current you can carry
The 32 A rating holds at 30 °C ambient. In a typical 40 °C panel, the continuous current drops to 30.4 A; at 50 °C it's 28.8 A; at 55 °C (the upper operating limit) it's 27.84 A. If you're populating a densely packed DIN rail or the panel runs warm, size the upstream protection against the derated figure, not the nameplate 32 A. The maximum power dissipation is 11.4 W, which adds to the enclosure's thermal budget.
Terminal capacity and wiring
Solid and stranded conductors from 0.75 mm² up to 35 mm² are accepted. That top end (35 mm²) is oversized for a 32 A device — it allows looping through or tapping a larger feeder without a separate terminal block. Installation depth is 70 mm, overall depth 77 mm. The unit is halogen-free and silicon-free, which matters for clean-room or semiconductor-adjacent installations where outgassing is restricted.