The Siemens 5SU9404-1KK25 is a SENTRON RCBO (RCD-operated circuit breaker) combining overcurrent and residual current protection in a single 18 mm wide module. Rated 25 A with a Type C tripping characteristic, 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, fitting standard distribution boards with a 1-module width.
Ratings and what they mean for fit
The 25 A rating is the continuous current at 30 °C ambient; at elevated panel temperatures the load must be derated — 23.5 A at 40 °C, 22.75 A at 45 °C, 21.75 A at 50 °C, and 20.25 A at 55 °C (–). The Type C characteristic trips at 5–10× rated current, suited for motor and transformer inrush where a Type B would nuisance-trip. The 10 kA breaking capacity is the maximum prospective fault current the device can safely interrupt — adequate for most residential and light commercial service entrances, but verify available fault current at the point of installation.
Installation and environment
Mounts in any position on a DIN rail, with an installation depth of 70 mm and overall depth of 77 mm. Accepts solid or stranded conductors from 0.75 to 35 mm². Ambient operating range is -25 to +45 °C; storage range extends to -40 to +75 °C. Rated IP20 with the distribution board installed and conductors connected. Touch protection is provided. Halogen-free and silicon-free construction.