The Siemens 5SU9356-1CR25 is a SENTRON RCBO — a combined RCD and MCB in one 2-module-wide (36 mm) package. It protects a single-phase final subcircuit against overload, short-circuit, and earth leakage in one device, saving a DIN-rail position versus separate units. The residual-current element trips at 30 mA, Type AC (sinusoidal AC faults only — not for pulsed DC or smooth DC faults). Energy limitation class 3 means it lets through less fault energy than class 1 or 2 devices, reducing arc damage downstream.
Depth is 77 mm, installation depth 70 mm — check your enclosure depth before panel layout; some shallow consumer units may need the 70 mm clearance. Mounts in any position. Supply can enter from top or bottom. IP20 rating applies only when installed in a distribution board with connected conductors — not rated for wet or dusty environments without an outer enclosure.
Thermal derating — the real-world current
At 40 °C the continuous current drops to 23.5 A; at 50 °C to 21.75 A. If your panel internal temperature runs hot — common in crowded enclosures or near other heat sources — size the upstream protection and cable accordingly. Insulation voltage rated 264 V, surge voltage resistance 4 kV.