What this 400 A MCCB delivers
The Siemens 3VA2340-5HL42-0KL0 is a SENTRON molded case circuit breaker (MCCB) rated for 400 A continuous current at 40 °C, with an ETU320 electronic trip unit for line protection. It handles fault currents up to 187 kA at 240 V and 121 kA at 415 V — enough headroom for high-fault panels without cascading upstream. The 4-pole design covers three-phase plus neutral, and the shunt trip (STL) auxiliary release lets you remote-trip it from a safety circuit or E-stop chain.
Where it fits in a panel
At 184 mm wide, 248 mm tall, and 110 mm deep, this MCCB bolts into a standard panel footprint — no oddball cutout. The 4-pole body needs the same phase-to-phase clearance as a 3-pole unit plus neutral lug space. It ships with 2 auxiliary switches, 1 trip alarm, and 1 electrical alarm switch (HQ version), so you get status feedback without adding external relays.
Thermal derating and real-world current
Rated 400 A straight up to 50 °C ambient — no derating needed in a typical ventilated enclosure. Above that, it drops to 385 A at 55 °C, 370 A at 60 °C, 355 A at 65 °C, and 340 A at 70 °C. If your panel runs hot near a drive bank or transformer, size the load side accordingly. Maximum power loss is 96 W, so keep ventilation paths clear.