400 A MCCB with ETU320 — what the ratings mean for your panel
The Siemens 3VA2440-6HL32-0AC0 is a 3-pole SENTRON molded case circuit breaker rated for 400 A continuous current (Iu) with an ETU320 electronic trip unit. The 242 kA breaking capacity at 240 V tells you this breaker can safely interrupt fault currents up to that level without upstream cascading — critical for high-fault installations like transformer secondaries or large motor control centers. At 415 V and 440 V the rating holds at 187 kA, dropping to 121 kA at 500 V and 40 kA at 690 V, so match the system voltage to the available fault current when specifying. The ETU320 is a basic electronic trip unit — no communication, no voltage trigger, no phase-failure detection, no ground-fault monitoring. It's sized for straightforward line protection where you need adjustable overload and short-circuit curves without the complexity of a full metering trip. The 2 auxiliary switches (HQ version) provide status feedback to the PLC or SCADA without an add-on module.
Temperature derating — don't lose capacity at the panel door
This breaker holds its full 400 A rating up to 50 °C ambient. Above that, the continuous current must be derated: 384 A at 55 °C, 376 A at 60 °C, 368 A at 65 °C, and 360 A at 70 °C. If your panel runs hot — near a drive cabinet or in a non-climate-controlled enclosure — factor that derating into the load schedule. The maximum operating temperature is 70 °C; storage range is -40 °C to 80 °C.
Mounting and integration — panel footprint
Dimensions are 138 mm wide, 248 mm high, 110 mm deep. The 3-pole frame mounts on a standard backplate or DIN-rail adapter (not included). No undervoltage release, no shunt trip — the auxiliary release design is 'without'. If you need remote tripping, plan for an external shunt or UVR module. The 63.5 W maximum power loss at full load should be factored into the panel thermal budget.