400 A MCCB with ETU350 — what the ratings mean for your panel
The Siemens SENTRON 3VA2340-5HN32-0AJ0 is a 3-pole molded case circuit breaker rated for a continuous current Iu of 400 A, with an ETU350 electronic trip unit configured for line protection. At 240 V it interrupts 187 kA — that is the short-circuit current rating (SCCR) at that voltage, meaning it can safely clear a fault up to that level without welding contacts or cascading damage upstream. At 415 V and 440 V the interrupting rating holds at 121 kA; at 500 V it drops to 75.6 kA, and at 690 V to 17 kA. The 400 A rating holds from 40 °C through 50 °C; above that it derates to 385 A at 55 °C, 370 A at 60 °C, 355 A at 65 °C, and 340 A at 70 °C. The rated insulation voltage Ui is 800 V.
Integration and mounting
The breaker measures 138 mm wide by 248 mm tall by 110 mm deep. It mounts on a DIN rail or directly to a panel backplate via its screw terminals. The front face carries an IP40 protection rating — suitable for enclosed panel installation where no water ingress is expected. The auxiliary contact configuration includes 2 auxiliary switches plus 1 trip alarm switch (HP version), which gives a clean signal back to the PLC or annunciator on trip events.
Trip unit and protection profile
The ETU350 is an electronic trip unit with adjustable long-time, short-time, instantaneous, and ground-fault protection bands — standard for selective coordination in distribution panels. Maximum power loss is 96 W at rated current, which matters for thermal management inside a sealed enclosure. The breaker has a trip indicator (mechanical flag) for visual confirmation of a trip event. It does not include undervoltage release, communication functions, phase failure detection, or ground-fault monitoring — this is a straightforward line-protection breaker, not a multifunction power monitor.