The Siemens 5SU9404-0KK16 is a SENTRON 5SU9-series RCD-operated circuit breaker — an RCBO combining overcurrent and residual current protection in a single 18 mm wide unit. Rated 16 A at AC with a Type B tripping characteristic (instantaneous magnetic release for short-circuit plus thermal overload), it breaks fault currents up to 10 kA per EN 60898 and IEC 60947-2. The 1P+N configuration protects one live pole while switching the neutral, and the AC fault-current type means it detects sinusoidal AC residual currents only — not pulsating DC or smooth DC, so match it to loads like resistive heaters or standard induction motors where the fault path is purely AC.
Current derating and ambient limits
The 16 A rating holds at 30 °C ambient. At 40 °C it derates to 15.04 A, at 45 °C to 14.56 A, at 50 °C to 13.92 A, and at 55 °C to 12.96 A. The operating ambient range is -25 to +45 °C; storage range is -40 to +75 °C. If the panel ambient exceeds 45 °C, the RCBO still functions but the continuous current must be reduced per the derating curve — a consideration for sealed enclosures or high-density DIN-rail layouts.
Installation and wiring
Mounts in any position on DIN rail; installation depth is 70 mm, overall depth 77 mm, height 125 mm, width 18 mm (one width unit). Accepts solid or stranded conductors from 0.75 mm² up to 35 mm². Supply can enter from either top or bottom. The IP20 rating applies when installed in a distribution board with conductors connected. Overvoltage category III, energy limiting class 3, and touch protection are built in. Halogen-free and silicon-free construction.