What this RCBO delivers
The Siemens SENTRON 5SU1654-0KK40 is a 2-pole (1P+N) residual-current circuit breaker with overcurrent protection — an RCBO — rated 40 A at AC with a Type B tripping characteristic. The B curve means it trips between 3 and 5 times rated current, suited for resistive and general-purpose loads where inrush is modest. Breaking capacity is 10 kA per EN 60898, which certifies it for fault interruption in residential and light commercial distribution boards up to that prospective short-circuit level. The RCBO detects AC fault currents only (Type AC). It occupies 2 width units (36 mm) on a DIN rail, with any mounting position allowed. Installation depth is 70 mm plus the 77 mm overall depth — factor that into enclosure sizing. Terminal capacity accepts solid or stranded conductors from 0.75 mm² up to 35 mm², covering most branch-circuit wiring.
Thermal derating and ambient limits
The 40 A rating holds at 30 °C ambient. Above that, the continuous current must be derated: 37.6 A at 40 °C, 36.4 A at 45 °C, 34.8 A at 50 °C, 32.4 A at 55 °C (which is the upper operating limit), and further down to 29.2 A at 70 °C. If the distribution board runs warm — say, alongside other heat-generating devices — use the 55 °C row as the realistic continuous figure. Operating ambient range is -25 °C to +55 °C; storage range extends to -40 °C to +75 °C.
Panel integration notes
Mounts on 35 mm DIN rail, any orientation. Supply can enter from top or bottom. The IP20 rating applies only when the distribution board is installed and conductors are connected — treat the device as unprotected until the enclosure is closed. Overvoltage category III means it is rated for fixed-installation downstream of the main distribution board. Energy limiting class 3 indicates good current-limiting performance for downstream equipment protection.