The Siemens 5SU1674-7AK82 is a SENTRON RCBO combining overcurrent protection and residual current detection in a single 4-pole device. Rated 125 A at 30 °C with a C-curve tripping characteristic and 300 mA Type B residual current sensitivity, it handles sinusoidal AC, pulsating DC, and smooth DC fault currents — the Type B rating is what you need for VFD, UPS, or EV charging circuits where pure DC leakage can blind a standard RCD. Breaking capacity is 10 kA per both EN 60898 and IEC 60947-2, so it clears line-to-neutral and line-to-earth faults up to that level without upstream cascading. The 4-pole design (4P) protects all live conductors; the neutral pole is switched and monitored.
Temperature derating and panel fit
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. The unit occupies 11 modular width units (198 mm wide) with a depth of 77 mm and an installation depth of 70 mm. IP20 rating applies once the distribution board is installed with connected conductors — this is a panel-internal device, not a weather-exposed one.