Above that, the thermal derating curve steps down: 385 A at 55 °C, 370 A at 60 °C, 355 A at 65 °C, and 340 A at 70 °C — so if your panel runs hot, that 400 A nameplate only holds in a 50 °C or cooler enclosure. The interrupting capacity hits 242 kA at 240 V AC and 187 kA at both 415 V and 440 V, then drops to 121 kA at 500 V and 7.5 kA at 690 V. That 7.5 kA at 690 V tells you this breaker is sized for high-fault 480 V or 600 V class systems, not for 690 V main service.
ETU320 trip unit and N-conductor protection
The overcurrent release is an ETU320 electronic trip unit — that's the base electronic trip in the 3VA2 platform, providing LSI protection curves (long-time, short-time, instantaneous) without ground-fault monitoring. The N-conductor protection is field-adjustable: OFF, 50%, or 100% of the phase rating, which matters for 4-wire systems where the neutral may carry harmonic currents.
The breaker measures 184 mm wide by 248 mm tall by 110 mm deep. That 184 mm width for a 4-pole frame is standard for the 3VA2 platform — it needs a full 4-module-wide cutout in the panel gland plate.