What this MCCB carries — and what it means on the line
The Siemens 3VA2340-5JP32-0KC0 is a SENTRON molded case circuit breaker rated for 400 A continuous current (Iu) at 40 °C, with an ETU550 electronic trip unit. That 400 A holds flat through 50 °C — only starts to derate at 55 °C (375 A) and steps down to 300 A at 70 °C, so in a warm panel you still get the full rating unless ambient pushes past 50 °C. The 3-pole frame carries a breaking capacity of 187 kA at 240 V, 121 kA at 415/440 V, 75.6 kA at 500 V, and 17 kA at 690 V — that's a high-interrupting-capacity frame, not a standard one, sized for fault levels near the transformer secondary or a large motor control center.
Trip unit and auxiliary hardware
The ETU550 is an electronic trip unit with communication capability — it can talk to a higher-level system for power monitoring and trip event logging, not just a dumb thermal-magnetic. The breaker ships with a shunt trip (STL) auxiliary release and two auxiliary switches (HQ type) pre-installed. That means you get remote trip capability and status feedback out of the box, no separate add-on kit to order. The auxiliary contact version is listed as 2 auxiliary switches HQ, so two form-C contacts for breaker position indication.
Panel fit and thermal management
Footprint is 138 mm wide by 248 mm tall by 110 mm deep — a standard 3-pole MCCB form factor that fits most distribution panel cutouts. The 96 W maximum power loss at full load means you need to account for heat dissipation in the enclosure; don't stack it tight against other high-loss devices without checking the internal temperature rise. Operating range is -25 °C to 70 °C, storage from -40 °C to 80 °C.
What the ratings mean for the buyer
The 400 A rating at 40 °C is the continuous current the breaker can carry without tripping in a 40 °C ambient. The 187 kA breaking capacity at 240 V means it can safely interrupt a fault current up to that level without failing catastrophically — that's the SCCR (short-circuit current rating) you'd use for a UL 508A panel label. The 800 V rated insulation voltage (Ui) tells you the internal clearances and creepage are designed for 800 V systems, so it's suitable for 480 V and 600 V class installations with margin.