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.
Current derating and ambient limits
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. 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
Supply can enter from either top or bottom. Overvoltage category III, energy limiting class 3, and touch protection are built in. Halogen-free and silicon-free construction.