Product identity and key ratings
The Siemens SENTRON 5SU1674-8AK81 is a 4-pole RCBO (residual current circuit breaker with overcurrent protection) in the Super Resistant K design, combining Type B residual current detection with a D tripping characteristic for overcurrents. Rated at 100 A (at 30 °C ambient) with a 300 mA residual fault current threshold, it provides both earth leakage and short-circuit/overload protection in a single modular device — a space-saving choice for distribution boards where separate RCCB and MCB would consume more width. Breaking capacity is 10 kA per both EN 60898 and IEC 60947-2, meaning it can safely interrupt fault currents up to that level without upstream cascading — sufficient for most commercial and light industrial sub-distribution boards.
Type B residual current and D-curve overcurrent — what they mean for the installation
Type B residual current detection covers smooth DC, pulsating DC, and AC residual currents — essential where variable-frequency drives, UPS systems, or rectifier loads are downstream, since those can generate DC fault currents that Type A or AC devices cannot detect. The D tripping characteristic (10–20× In magnetic trip) is designed for loads with high inrush currents — typically transformers, welding equipment, or motor starters — where a B or C curve would nuisance-trip on startup. Temperature derating is published: 100 A at 30 °C, 92.5 A at 40 °C, 89 A at 45 °C, 85 A at 50 °C, 81 A at 55 °C, and 77 A at 60 °C — the panel designer must apply these when the RCBO is enclosed or in a warm environment.
Physical fit and panel integration
Width is 198 mm (11 modular width units), depth 77 mm, height 90 mm, with an installation depth of 70 mm — it occupies a standard DIN-rail footprint but at 11 MW is wider than a typical 4-pole MCB (usually 4 MW), so verify available rail space before panel layout. Mounting position is any; supply can enter from top or bottom, which simplifies busbar and cable routing in crowded enclosures. IP20 rating applies when installed in a distribution board with connected conductors — the RCBO itself is not sealed for wet or dusty environments; it belongs inside a panel.