400 A MCCB with ETU550 — what the ratings mean for your panel
The Siemens SENTRON 3VA2340-5JP32-0JC0 is a 3-pole molded case circuit breaker (MCCB) rated for a continuous current Iu of 400 A, fitted with an ETU550 electronic trip unit for line protection. The 400 A rating holds at ambient temperatures up to 50 °C; above that, it derates to 375 A at 55 °C, 350 A at 60 °C, 325 A at 65 °C, and 300 A at 70 °C — so if the breaker lives in a warm enclosure, the effective ampacity is the derated figure, not the nameplate number. Breaking capacity is 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 — enough for high-fault utility feeds or transformer secondaries. The 800 V rated insulation voltage (Ui) confirms it is built for 690 V line-to-line systems with margin. The ETU550 trip unit supports communication and includes a shunt trip (STL) auxiliary release, plus two auxiliary switches HQ. This means the breaker can be remotely tripped and its status reported back to a PLC or BMS — useful for emergency-off circuits or load-shedding schemes. The 15 000 mechanical endurance cycles suit frequent switching applications like capacitor bank or motor feeder duty.