The Siemens SENTRON 5SU1356-0KK40 is a 2-pole (1P+N) residual current operated circuit breaker (RCBO) combining overcurrent protection and residual current detection in a single 36 mm wide (2 modular width units) device for 50 Hz systems. Rated 40 A at 30 °C with a Type B tripping characteristic, it interrupts overcurrents per EN 60898 up to 6 kA and per IEC 60947-2 up to 10 kA, with a residual current type AC (sinusoidal) — suited for general-purpose final circuits in residential and commercial distribution boards.
Temperature derating — what the 40 A rating actually means in a warm panel
At 40 °C the continuous current drops to 37.6 A, at 50 °C to 34.8 A, and at 70 °C to 29.2 A. If the distribution board sits in a warm environment or is tightly packed, size the load side accordingly — the nameplate 40 A is not the usable figure at elevated panel temperature.
Width of 36 mm (2 MW), depth of 77 mm, and installation depth of 70 mm.