The Siemens 5SU1324-6FR20 is a 2-pole RCBO from the SENTRON series, combining overcurrent and residual current protection in a single 36 mm wide unit. Rated 20 A at 30 °C with a B-curve tripping characteristic and 30 mA residual current sensitivity, it is designed for final-circuit protection in residential and commercial distribution boards.
Ratings and derating
The 20 A rating holds at 30 °C ambient. At 40 °C it derates to 19.5 A, at 50 °C to 18.9 A, and at 60 °C to 18.4 A — so if the panel runs hot, size the upstream protection for the derated value, not the 30 °C figure. The 10 kA breaking capacity per EN 60898 means it can safely interrupt a short-circuit fault up to that level, which covers most domestic and light commercial service entrances.
Residual current and selectivity
Type A residual current detection handles sinusoidal AC and pulsating DC fault currents, which covers modern electronics and single-phase rectified loads. The 30 mA trip threshold is the standard for personal protection against electric shock. The super resistant K design indicates enhanced immunity to nuisance tripping from surge currents and voltage transients — useful on lines with switching power supplies or motor drives.
Mounting and integration
Occupies 2 modular width units (36 mm) on a DIN rail. Depth is 72 mm, installation depth 70 mm — confirm the gland plate clearance if the board is shallow. Mounting position is any; supply can enter from top or bottom. IP20 rated once installed in a distribution board with conductors connected.