What this RCBO is and where it fits
The Siemens SENTRON 5SU9406-0KK25 is a 1P+N RCD-operated circuit breaker — an RCBO — combining overcurrent and residual-current protection in a single 18 mm wide modular unit. Rated 25 A at 30 °C with a B tripping characteristic, it interrupts fault currents up to 6 kA per EN 60898 and IEC 60947-2. The 1P+N design switches the phase and monitors the neutral, protecting one live conductor while the neutral is switched but not protected. This makes it a direct fit for single-phase final circuits in DIN-rail distribution boards where space is tight — one module width per pole saves rail length.
Ratings that govern the real application
The 25 A rating at 30 °C is the headline number, but the derating curve matters more in a warm panel: at 40 °C it's 23.5 A, at 45 °C it's 22.75 A, at 50 °C it's 21.75 A, and at 55 °C it's 20.25 A. If your enclosure ambient runs above 40 °C, size the circuit for the derated current — not the 25 A sticker. The 6 kA breaking capacity (both EN 60898 and IEC 60947-2) is adequate for most domestic and light commercial sub-distribution boards; verify the prospective short-circuit current at the installation point stays under that. The B curve (3–5 In instantaneous trip) suits resistive and general-purpose loads — lighting, small appliances, control transformers — where inrush is low. For motor or capacitor loads, a C or D curve would be the better call.
Panel integration notes
Mounts on standard DIN rail in any position. One modular width (18 mm) per unit, 77 mm depth, 125 mm height. Installation depth is 70 mm — factor that into enclosure depth, especially with wiring ducts. Supply can enter from top or bottom. Rated IP20 only when installed in a distribution board with conductors connected — not for open-panel or washdown environments. Halogen-free and silicon-free construction matters for clean-room or high-reliability installations where outgassing can contaminate contacts or optics.