400 A MCCB with ETU560 — selectivity and coordination anchor
The Siemens SENTRON 3VA2340-5JQ32-0AJ0 is a 3-pole molded case circuit breaker rated 400 A continuous current, carrying the full 400 A from 40 °C up through 50 °C before the thermal derating curve starts — at 55 °C it holds 375 A, at 60 °C 350 A, and at 70 °C 300 A. That means for a panel designed around a 400 A bus, you get full rating without oversized enclosure ventilation up to 50 °C ambient. Breaking capacity peaks at 187 kA at 240 V, drops to 121 kA at 415 V and 440 V, then to 75.6 kA at 500 V, and 17 kA at 690 V.
If you're replacing an older 3VA2 frame, verify the auxiliary contact wiring scheme matches your existing control circuit.
Integration and panel fit
Dimensions are 248 mm height, 138 mm width, 110 mm depth. The 138 mm width means it occupies three 45 mm pole spaces on the DIN rail or mounting plate. The ground fault monitoring uses summation current formation on the L-conductor — that's a residual-current measurement method that detects ground faults by summing the phase currents, not by a separate toroid on the neutral. This matters if your system is a 3-wire delta without a neutral conductor.
Maximum power loss is 96 W at full rated current. That's the heat you need to extract from the enclosure — for a panel with multiple breakers at 400 A, the cumulative heat load drives the ventilation or air-conditioning sizing. The derating curve above 50 °C is the practical limit: if your panel ambient hits 70 °C, you can only load this breaker to 300 A. The storage range is wider — that's the limit for warehousing or shipping without climate control, not for running.