400 A MCCB with ETU350 — what the ratings mean for fit
The Siemens 3VA2340-5HN32-0DH0 is a 3-pole SENTRON molded case circuit breaker (MCCB) rated for line protection, carrying a continuous current Iu of 400 A at 40 °C through 50 °C ambient — it holds that full rating without derating up to 50 °C, then steps down to 385 A at 55 °C and 340 A at 70 °C. That thermal profile matters if this breaker sits in a crowded panel or near other heat sources; the 98.5 W maximum power loss also needs to be factored into the enclosure's thermal budget. Breaking capacity is the headline: 187 kA at 240 V AC, 121 kA at 415/440 V, 75.6 kA at 500 V, and 17 kA at 690 V. These are the maximum fault currents this breaker can safely interrupt — if your available fault current at the panel is below those thresholds, this unit clears it without upstream cascading. The ETU350 electronic trip unit gives adjustable long-time, short-time, and instantaneous protection curves, plus ground-fault capability (though this variant ships without the ground-fault module fitted). An undervoltage release (UVR) is integrated as standard — part number 3VA9608-0BB25 — so this breaker trips automatically if the control voltage drops below the dropout threshold. The auxiliary contact configuration is 2 auxiliary switches plus 1 trip alarm switch (HQ designation), giving three separate signal paths for status feedback to a PLC or annunciator panel.
Panel fit and integration
Dimensions are 248 mm high, 138 mm wide, 110 mm deep — a standard MCCB footprint for the 400 A frame class. Mounting is via four screws to a backplate or DIN-rail adapter. Rated insulation voltage Ui is 800 V, so this breaker is suitable for 690 V line-to-line systems with margin. Operating temperature range is -25 °C to +70 °C; storage range is -40 °C to +80 °C. The 15 000 mechanical endurance cycles (latching) are typical for a fixed-mounted MCCB at this frame size — not a daily-switching device, but fine for backup protection and infrequent maintenance isolation.