What the ratings mean for fit
The 3VA2340-7HN42-0AA0 is a Siemens SENTRON molded case circuit breaker rated for 400 A continuous current with an ETU350 electronic trip unit. The 4-pole configuration handles three-phase plus neutral protection, common for main incomers or feeder breakers in 400 V distribution panels. Breaking capacity is 330 kA at 240 V, 242 kA at 415 V and 440 V, 187 kA at 500 V, and 7.5 kA at 690 V — the steep drop above 500 V means this breaker is sized for low-voltage main distribution, not 690 V motor circuits. The ETU350 is a programmable electronic trip unit with LSI (long-time, short-time, instantaneous) protection curves, adjustable via the front interface, so coordination studies can be dialed in without swapping trip packs.
Temperature derating — the real-world current
The 400 A rating holds at 40 °C, 45 °C, and 50 °C. Above that, derate linearly: 385 A at 55 °C, 370 A at 60 °C, 355 A at 65 °C, and 340 A at 70 °C. If the panel ambient runs at 55 °C, the breaker delivers 385 A continuous — not 400 A. The maximum operating temperature is 70 °C; storage range is -40 °C to 80 °C. Power loss at full load is 96 W maximum, which factors into enclosure ventilation sizing.
Panel integration and dimensions
Mounts on a DIN rail or direct panel-mount via the MCCB footprint. Dimensions: 248 mm height, 184 mm width, 110 mm depth. The 184 mm width is for a 4-pole frame — verify the panel cutout or mounting plate accommodates that before committing the BOM. No undervoltage release, no voltage trigger, no communication function, and no ground-fault monitoring — this is a bare line-protection breaker; add accessories separately if needed.