What it is and what it does
The Siemens 5SU1324-6KX32 is a 2-pole RCBO (residual-current circuit breaker with overcurrent protection) from the SENTRON family, combining a Type B MCB and a 30 mA residual-current device in one 3-module-wide (54 mm) package. It's rated 32 A at 30 °C with a 10 kA breaking capacity per EN 60898, so it handles both overload and earth-fault protection in a single DIN-rail slot — no separate RCD needed downstream. The Type B curve trips instantaneously on short-circuit above 3 to 5 times rated current, which suits resistive and lightly inductive loads in commercial or industrial sub-distribution boards.
Thermal derating — what the numbers mean in a real panel
The 32 A rating holds at 30 °C ambient, but drops to 30.4 A at 40 °C and 24.64 A at 70 °C. That matters when this RCBO sits in a crowded enclosure with other heat sources: if your load pulls 28 A continuous and the panel ambient hits 55 °C, the 27.84 A derated capacity means you need to upsize the device or improve ventilation. The derating curve is published, so you can size it properly at the design stage rather than chasing nuisance trips in the field.
Mounting and integration
Mounts on standard DIN rail in any orientation — the mounting position is unrestricted. Depth is 77 mm (70 mm installation depth), which fits typical distribution boards without crowding the gland plate. The 54 mm width (3 modular units) means it occupies three 18 mm slots; plan your rail fill accordingly if you're retrofitting into an existing board. Supply can enter from top or bottom, which simplifies rework when the busbar layout is already set.