It delivers a breaking capacity of 330 kA at 240 V, tapering to 242 kA at 415 V and 440 V, then 187 kA at 500 V, and 9 kA at 690 V — the 690 V figure is the one to watch for 690 V line-side faults; at that voltage the breaker is still adequate for most downstream coordination but the margin narrows. The ETU860 provides adjustable N-conductor protection (OFF, 20 % to 130 %) and ground-fault monitoring via summation current formation on L+N, so it handles both phase and residual current detection without a separate module.
Thermal derating and integration
The breaker carries its full 400 A rating up to 50 °C ambient; above that it derates to 376 A at 55 °C, 352 A at 60 °C, 324 A at 65 °C, and 300 A at 70 °C. For a panel builder, that means a 400 A bus can be served without oversizing the breaker as long as the enclosure ambient stays under 50 °C — beyond that, the derating curve governs the actual ampacity. The maximum power loss is 63.3 W, so ventilation or spacing in a sealed enclosure should account for that heat.