400 A MCCB with ETU350 — what the ratings mean for your panel
The Siemens SENTRON 3VA2340-5HN32-0JA0 is a 3-pole molded case circuit breaker rated for 400 A continuous current from 40 °C through 50 °C, meaning it holds its full nameplate rating without derating across typical panel ambient temps — you don't lose headroom just because the enclosure runs warm. Above 50 °C it derates stepwise: 385 A at 55 °C, 370 A at 60 °C, 355 A at 65 °C, and 340 A at 70 °C (–). That thermal curve matters when you're packing breakers into a tight switchboard; the 400 A frame gives you a real-world cushion before you need to step up a frame size. Breaking capacity is the headline number for fault coordination: 187 kA at 240 V, 121 kA at 415 V and 440 V, 75.6 kA at 500 V, and 7.5 kA at 690 V (–). That 187 kA at 240 V is a high-interrupting rating — it handles faults on large transformer secondaries or high-capacity busways without needing a current-limiting fuse upstream. The 121 kA at 415 V covers most industrial distribution in North America and Europe on a 400 V class system, giving you full selectivity headroom downstream. The ETU350 electronic trip unit gives adjustable long-time, short-time, and instantaneous pickup settings — it's not a fixed thermal-magnetic, so you can coordinate selectively with downstream breakers on a panel schedule. Line protection version means it's configured for feeder protection, not motor or generator duty. No auxiliary contacts, no undervoltage release, no ground-fault monitoring on this variant — if you need those, you're looking at a different suffix.
Mounting and integration — fits standard 3-pole MCCB footprint
Dimensions are 248 mm high, 138 mm wide, 110 mm deep — that's 9.76 by 5.43 by 4.33 inches. It's a standard SENTRON 3VA frame size; bolt it onto a DIN rail or panel-mount plate in a distribution board. The IP40 front protection means it's fine for indoor panel use but not washdown areas — keep it inside the enclosure. Power loss is 96 W maximum — that's the heat you need to vent in a sealed enclosure. For a panel with several breakers at this frame size, factor that into your thermal calculation; it's not trivial. Operating temperature range is -25 °C to 70 °C, storage from -40 °C to 80 °C.