The Siemens 5SU1674-7CK82 is a 4-pole RCBO from the SENTRON Super resistant K series — a combined overcurrent and residual current device that fits a standard DIN-rail distribution board. The Type B residual current detection handles smooth DC, pulsating DC, and AC fault currents up to 300 mA, which means it covers variable-speed drives, UPS systems, and EV charging circuits where pure AC or pulsating DC RCDs would be blind to a DC fault component.
Temperature derating — the real continuous current
At 40 °C it derates to 115.62 A, at 45 °C to 111.25 A, at 50 °C to 106.25 A, at 55 °C to 101.25 A, and at 60 °C to 96.25 A. If the distribution board runs warm — typical in a crowded panel — the actual continuous current the RCBO can carry without nuisance tripping is lower than the label. Size the upstream conductor and load accordingly.
At 11 modular width units (198 mm wide, 77 mm deep, 90 mm tall), it takes up a full 11-pole slot on the rail.