What this MCCB is and what it does
The Siemens 3VA2340-7HN32-0AH0 is a SENTRON molded case circuit breaker (MCCB) sized for line protection in distribution panels. It carries a rated continuous current Iu of 400 A across three poles, with an ETU350 electronic trip unit that gives adjustable long-time, short-time, instantaneous, and ground-fault protection curves — though this variant ships without ground-fault monitoring. The interrupting ratings are substantial: 330 kA at 240 V, 242 kA at 415 V and 440 V, 187 kA at 500 V, and 52.5 kA at 690 V. That means it can safely clear fault currents up to those levels without upstream devices needing to coordinate — a real advantage when you're trying to keep selectivity in a high-fault panel.
Thermal derating and enclosure fit
This breaker holds its full 400 A rating up to 50 °C ambient. Above that it derates in 5 °C steps: 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 — say a packed MCC bucket near a transformer — that 340 A at 70 °C figure is the one to design for, not the nameplate 400 A. The enclosure footprint is 248 mm high by 138 mm wide by 110 mm deep, which fits the standard SENTRON 3VA mounting pattern. IP40 on the front means it's protected against tools and wires >1 mm, but it's not sealed against water ingress — keep it inside the enclosure, not on a washdown wall.