It protects a single-phase final subcircuit against overload, short-circuit, and earth leakage in one go, saving a DIN-rail slot over separate MCB + RCCD. The 30 mA residual sensitivity (Type A) catches pulsating DC fault currents from electronics and VFDs — the sort of leakage you get from a variable-speed drive feeding a bearing-lube pump out here in the grease.
At 40 °C it derates to 18.8 A, at 45 °C to 18.2 A, at 50 °C to 17.4 A, and at 55 °C to 16.2 A. If your panel runs hot near a drive cabinet or a motor junction box, size the load to the derated number — don't count on the full 20 A above 30 °C. That's the right choice for a mixed load with some inductive kick. The design is instantaneous (no intentional delay), so it clears earth faults fast — important for personnel protection on a 30 mA RCD. The energy limitation class 3 keeps let-through energy low, protecting downstream wiring and connected gear.
Two modular width units (36 mm) — check your panel fill factor; it takes the space of two single-pole MCBs. Supply can come from either top or bottom, which saves rework when you're wiring a crowded gland plate. IP20 with the distribution board installed and conductors connected; that's the standard for enclosed panels, not for open washdown areas.