Thermal derating — the real-world current you can actually run
The 20 A rating holds flat from 40 °C to 50 °C — that's your full nameplate current in a warm panel. At 55 °C it derates to 19.2 A, at 60 °C to 18.8 A, at 65 °C to 18.4 A, and at 70 °C to 18 A. If your panel ambient runs above 50 °C, size the load-side conductors and downstream protection for the derated value, not the 20 A label. The rated insulation voltage Ui is 800 V, so the breaker is comfortable in 480 V or 600 V systems without voltage derating.