400 A MCCB with 187 kA interrupting capacity — selectivity anchor for high-fault panels
The Siemens SENTRON 3VA2340-5JQ32-0JL0 is a 3-pole molded case circuit breaker rated for 400 A continuous current (Iu) and a rated insulation voltage of 800 V. Its headline interrupting ratings — 187 kA at 240 V, 121 kA at 415 V and 440 V, 75.6 kA at 500 V, and 17 kA at 690 V — mean this breaker can clear a bolted fault at those levels without rupturing, which is the deciding factor for main or feeder positions in high-capacity distribution switchboards where upstream transformer impedance is low. The electronic ETU560 trip unit provides adjustable long-time, short-time, instantaneous, and ground-fault protection curves, making it suitable for selective coordination downstream of a larger main breaker. The breaker includes a shunt trip (STL) release for remote tripping, a communication function for integration into energy management systems, and an auxiliary contact configuration of 2 auxiliary switches plus 1 trip alarm switch plus 1 electrical alarm switch. It does not include an undervoltage release or phase failure detection, so those functions must be added externally if required.
Thermal derating and panel integration
Rated at 400 A from 40 °C through 50 °C ambient, the breaker derates to 375 A at 55 °C, 350 A at 60 °C, 325 A at 65 °C, and 300 A at 70 °C. For a panel builder, this means the 400 A frame can be loaded to its full rating in a 50 °C enclosure without forced ventilation, but above that temperature the continuous current must be reduced per the curve. The 110 mm depth, 138 mm width, and 248 mm height fit standard MCCB mounting footprints; verify the busbar connection centers against the existing panel layout. Maximum power loss is 96 W, which contributes to the enclosure heat load — account for this when sizing ventilation or cooling for a multi-breaker lineup. The operating temperature range is -25 °C to 70 °C; storage range is -40 °C to 80 °C.