What this 400 A MCCB delivers
The Siemens 3VA2340-5KP32-0BC0 is a SENTRON molded case circuit breaker rated for 400 A continuous at 40 °C, with the ETU850 electronic trip unit handling line protection across a 3-pole configuration. Breaking capacity hits 187 kA at 240 V, 121 kA at 415 V, and 75.6 kA at 500 V — enough headroom for high-fault utility feeds or transformer secondaries where SCCR coordination matters. The ETU850 release supports communication functions, meaning this breaker can talk to a BMS or PLC for remote trip indication and load monitoring — not just a dumb overcurrent device. Power loss runs 98.5 W at full load, so factor that into enclosure ventilation if you're packing multiple breakers in a tight panel.
Thermal derating and ambient limits
Full 400 A holds from 40 °C through 50 °C, then steps down: 375 A at 55 °C, 350 A at 60 °C, 325 A at 65 °C, and 300 A at 70 °C. If your panel ambient runs hot, that 70 °C figure is the floor — still 300 A available. Operating range spans -25 °C to 70 °C; storage handles -40 °C to 80 °C. The storage limit governs shipping and idle spares, not running conditions.
Physical fit and auxiliary wiring
Dimensions are 248 mm high, 138 mm wide, 110 mm deep — standard SENTRON 3VA frame size for this current class. Verify the mounting footprint against your existing busbar or cable lug layout before ordering. Comes with 2 HQ auxiliary switches and an undervoltage release (UVR) integrated. The UVR design means the breaker trips on loss of control voltage — common for emergency-stop chains or undervoltage protection schemes. No ground-fault monitoring on this variant, and no phase-failure detection built into the trip unit. If those are required, look at the 3VA2 with GF or the ETU860 option.