400 A MCCB with ground-fault and comms — what you need to know
The Siemens SENTRON 3VA2340-8KQ32-0AA0 is a 3-pole molded case circuit breaker rated 400 A continuous at 40 °C, designed for line protection in distribution panels. It carries a trip unit adjustable from 600 A to 4 000 A, so you can fine-tune the overload threshold to match your transformer or feeder without swapping hardware. Breaking capacity hits 440 kA at 240 V and 330 kA at 415 V — enough headroom for high-fault installations where a standard MCCB would cascade upstream. This breaker includes communication capability and ground-fault monitoring via summation current formation on the L-conductor, making it a fit for networked power distribution where you want remote trip indication and leakage detection without a separate relay. The 800 V rated insulation voltage supports 690 V line-to-line systems comfortably.
Breaking capacity across voltage levels
The interrupting rating drops as voltage rises — expected for any MCCB. At 240 V it clears 440 kA; at 415 V and 440 V it holds 330 kA; at 500 V it still manages 220 kA; at 690 V it's 52.5 kA. For a 400 A frame these are strong numbers, especially the 330 kA at 415 V — typical for large transformer secondaries or industrial service entrances where fault current can exceed 200 kA.
Thermal derating and power loss
The breaker carries 400 A up to 50 °C ambient. Above that it derates: 375 A at 55 °C, 350 A at 60 °C, 325 A at 65 °C, and 300 A at 70 °C. If your panel runs hot — near a transformer or in a non-climate-controlled enclosure — factor in the 55 °C or 60 °C column. Maximum power loss is 96 W at full load, so consider ventilation or forced air if you're packing multiple breakers in a tight cabinet. Operating temperature range is -25 °C to 70 °C; storage range is -40 °C to 80 °C. The storage limit matters if you're holding spares in a non-conditioned warehouse — keep them above -40 °C and below 80 °C and they'll be fine on the shelf for years.