What it is and what it does
The Siemens 3VA2440-5KP42-0AA0 is a SENTRON molded case circuit breaker (MCCB) rated for 400 A continuous current across the full ambient range from 40 °C to 70 °C — no derating needed up to that ceiling. Four poles, with an ETU850 electronic trip unit designed for line protection. Insulation voltage rated at 800 V. The interrupting ratings climb to 187 kA at 240 V, 121 kA at 415/440 V, 75.6 kA at 500 V, and 9 kA at 690 V, so it handles high-fault utility feeds and transformer secondaries without cascading upstream. The ETU850 trip unit is a communicating electronic release — this breaker carries a communication function for integration into a monitoring or energy-management system. Maximum power loss is 63.5 W, which matters for enclosure thermal budgeting when multiple breakers are ganged. Physical footprint: 248 mm tall, 184 mm wide, 110 mm deep. Mounts in standard panel or enclosure backpan layouts; the 4-pole width is the dimension to check against existing busbar or cable ladder spacing.
What the ratings mean for fit
The 400 A continuous rating is flat across the ambient range — that is unusual and means no thermal derating curve to manage in warm enclosures. The interrupting range (600 A minimum to 6 000 A maximum) covers most distribution panelboard and motor control center applications. The 187 kA at 240 V is a very high SCCR; this breaker can sit on the secondary of a large 480 V–208Y/120 V transformer without needing a current-limiting fuse upstream. The ETU850 electronic trip unit provides adjustable long-time, short-time, instantaneous, and ground-fault protection curves (ground-fault monitoring version: without). The communication function allows remote trip indication and current monitoring via a compatible bus system, useful for energy management or predictive maintenance setups.