Interrupting capacity and thermal derating
Interrupting capacity drops with system voltage: 187 kA at 415 V and 440 V, 121 kA at 500 V, and 4.5 kA at 690 V. Thermal derating is minimal up to 50 °C (full 250 A). Above that, the breaker linearly derates to 213 A at 70 °C ambient. In a crowded panel with multiple breakers ganged, that 70 °C ceiling is the practical limit for continuous load.
