The 5SU9356-1CN25: Rated 25 A at 30 °C ambient, but the thermal derating curve is published: 23.3 A at 40 °C, 22 A at 45 °C, 21.5 A at 50 °C, 20.8 A at 55 °C. If your enclosure runs warm — typical near a furnace controller or in a crowded panel — size the load to the derated value, not the 30 °C number. The C-curve (magnetic trip at 5–10× In) handles motor inrush and transformer loads without nuisance tripping on startup. The 30 mA AC residual-current trip (type AC) protects against sinusoidal earth faults — standard for general-purpose circuits, but not for pulsating DC or smooth DC faults (those need type A or F).
Deployment context
At 36 mm wide (2 MWU), it fits standard modular enclosures. The 77 mm depth (70 mm installation depth) leaves clearance for wiring behind the DIN rail.