The Siemens 5SU9356-7KN32 is a 2-module-wide (36 mm) RCD-operated circuit breaker — an RCBO — from the SENTRON 5SU9 series. It combines overcurrent protection (MCB function) with residual current detection in a single DIN-rail unit, saving a slot compared to separate breaker + RCD. The Type A fault-current sensitivity means it catches pulsating DC residual currents from electronics or rectifier loads — not just pure sinusoidal AC faults — which is the standard pick for modern panels with switched-mode supplies.
Breaking capacity — which number governs your installation
For a panel builder, the practical takeaway: if your declared SCCR at the board is 6 kA or less, this unit meets it under EN 60898; if the board is rated 10 kA, you rely on the IEC 60947-2 rating — verify the installation category and upstream protection coordination.
Depth is 77 mm (installation depth 70 mm), so it clears a standard 80 mm-deep enclosure backplate without crowding. Conductor range: solid or stranded 0.75 to 35 mm² — that 35 mm² upper end handles the full 32 A without needing a ferrule or reducing tail. Supply can enter from top or bottom, which simplifies busbar routing in a crowded board. IP20 with conductors connected and distribution board installed — no washdown rating, so keep it inside the panel.
Thermal derating — the real-world current
At 40 °C it derates to 30.08 A; at 45 °C to 29.12 A; at 50 °C to 27.84 A; at 55 °C to 25.92 A. For a 32 A circuit, a 45 °C ambient knocks off nearly 3 A. Plan the load accordingly or move the RCBO to a cooler zone in the board.