What it is and what it does
The Siemens 5SU9404-0KK10 is a SENTRON RCD-operated circuit breaker — an RCBO that combines overcurrent protection and residual current detection in one 18 mm-wide module. It protects a single-phase final subcircuit at 10 A rated current with a Type B tripping characteristic, meaning it handles both resistive and moderate inductive loads without nuisance trips. The breaking capacity is 10 kA per EN 60898 and IEC 60947-2, so it safely clears faults up to that level in a standard distribution board. Rated voltage is AC only, 1P+N configuration with one protected pole.
Thermal derating — the real current you get
The 10 A rating holds at 30 °C ambient. At 40 °C it derates to 9.4 A, at 45 °C to 9.1 A, at 50 °C to 8.7 A, and at 55 °C to 8.1 A. If this breaker sits in a crowded panel where ambient runs above 40 °C, size the load for the derated figure, not the nameplate 10 A. Operating range is -25 to +45 °C; storage range is -40 to +75 °C.
Wire range and panel fit
Terminals accept 0.75 to 35 mm² solid or stranded copper — covers everything from a 1.5 mm² lighting circuit to a 10 mm² feeder. The breaker is 18 mm wide (one width unit), 125 mm tall, 77 mm deep with a 70 mm installation depth. Mounts in any position, which simplifies layout in tight enclosures. IP20 with conductors connected and the distribution board installed.
Compliance and approvals
Rated overvoltage category III, energy limiting class 3. Designed per EN 60898 and IEC 60947-2 for the 10 kA breaking capacity. Halogen-free and silicon-free construction. Touch protection is built in. The product is classified as F per DIN EN 61346-2 and DIN EN 81346-2. Power supply cord position can be top or bottom — no orientation restriction.