400 A MCCB with ETU850 — what the ratings mean for fit
The Siemens 3VA2340-5KP32-0AA0 is a SENTRON molded case circuit breaker rated for 400 A continuous current at 40 °C through 50 °C, with no derating needed across that band. Above 55 °C the curve steps down: 375 A at 55 °C, 350 A at 60 °C, 325 A at 65 °C, and 300 A at 70 °C. That means if your panel ambient runs 55 °C or higher, the breaker's effective rating drops — size the load accordingly or plan for forced ventilation. The ETU850 electronic trip unit gives adjustable overload and short-circuit protection; the trip range spans 600 A minimum to 4 000 A maximum, so it covers a wide band of downstream fault levels without swapping the breaker body. Breaking capacity is 187 kA at 240 V, 121 kA at 415 V and 440 V, 75.6 kA at 500 V, and 7.5 kA at 690 V. That 187 kA at 240 V tells you this breaker is built for high-fault installations — think transformer secondaries or large motor control centers where available fault current is substantial. At 690 V the 7.5 kA rating is lower, so verify your system's prospective short-circuit current at that voltage level before specifying. Three-pole design, line protection configuration, and IP40 on the front face. The 800 V rated insulation voltage (Ui) gives headroom for 690 V systems. Max power loss is 96 W — that's the heat the breaker dumps into the enclosure; factor it into your thermal budget if the panel is tightly packed.
Integration and mounting
Dimensions: 248 mm height, 138 mm width, 110 mm depth. That 138 mm width is the 3-pole footprint — it fits standard SENTRON 3VA mounting plates and busbar systems. Depth of 110 mm means it clears most shallow enclosures, but check gland-plate clearance if you're back-paneling with a rear cover. Operating temperature range is -25 °C to 70 °C; storage range is -40 °C to 80 °C. The ETU850 includes a communication function — that means it can talk to a higher-level system (PROFIBUS, PROFINET, or Modbus via the SENTRON communication modules) for remote trip indication, current monitoring, and parameter adjustment. No undervoltage release and no voltage trigger on this variant; ground-fault monitoring is also absent. If you need those, look at the 3VA2 options with the appropriate suffix.