What this 400 A MCCB is and what it does
The Siemens SENTRON 3VA2340-5HM42-0AA0 is a 4-pole molded case circuit breaker rated for 400 A continuous current, designed for line protection in distribution panels and industrial switchgear. Its 800 V rated insulation voltage means it's built for 690 VAC systems with margin — common in heavy industrial plants running 400–690 V motor control centers. Breaking capacity is the headline: 187 kA at 240 VAC, 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 tells you this breaker handles high-fault utility feeds or transformer secondaries where available fault current is extreme — not every MCCB in this frame size carries that. The 121 kA at 415 V covers most European and Asian industrial mains. Thermal derating is published: full 400 A up to 50 °C ambient (–), then 385 A at 55 °C, 370 A at 60 °C, 355 A at 65 °C, 340 A at 70 °C. If your panel runs hot — say a sealed enclosure near a furnace line — that 340 A at 70 °C is the number to spec against, not the 400 A nameplate. Ground-fault monitoring uses summation current formation on L + N conductors — it watches the vector sum of line and neutral, so it catches leakage to ground without a separate GFCI module. That's useful for equipment protection on solidly-grounded wye systems where you want to trip on ground faults but don't need a dedicated relay.
Panel fit and mounting
Dimensions: 248 mm tall, 184 mm wide, 110 mm deep. That 184 mm width for a 4-pole 400 A frame is standard — it occupies the same footprint as other SENTRON 3VA2 breakers in this rating class. The 110 mm depth means it clears a 200 mm deep enclosure with room for rear bus connections. Maximum power loss is 96 W — that's the heat you need to vent in the enclosure. For a sealed panel, factor that into the thermal calculation; for a ventilated one, it's manageable. Operating range is -25 °C to 70 °C; storage from -40 °C to 80 °C.