400 A MCCB with TM240 Release
The Siemens 3VA1340-5EF42-0AA0 is a SENTRON molded case circuit breaker rated for 400 A continuous at 40 °C, built for line protection in a 4-pole configuration. It carries a TM240 thermal-magnetic overcurrent release, meaning the thermal pickup and magnetic trip are set for a 400 A frame — no electronic adjustment, just reliable bimetal and solenoid response for motor and feeder circuits. The interrupting ratings are serious: 187 kA at 240 V, 121 kA at 415 V, and still 11.9 kA at 690 V, so it handles high-fault utility feeds or transformer secondaries without needing a current-limiting fuse upstream.
Current Carrying and Thermal Derating
This breaker holds 400 A all the way up to 50 °C ambient. Above that it derates in steps: 392 A at 55 °C, 384 A at 60 °C, 376 A at 65 °C, and 367 A at 70 °C. If your panel runs hot — say next to a drive cabinet or a bank of contactors — you need to account for that drop. The maximum power loss is 92.1 W, so ventilation matters in a sealed enclosure.
Lifecycle and Sourcing
The lifecycle stage is marked as current, so Siemens still builds this order code. No end-of-life notice or successor has been issued for the 3VA1340-5EF42-0AA0. For a BOM freeze or a panel that's already been laid out, this part is specified and quoted to order against an RFQ through independent distribution. Availability and current pricing are confirmed at quote time.
Panel Fit and Environment
Dimensions are 248 mm high, 184 mm wide, and 110 mm deep — a standard MCCB footprint for a 400 A frame. The front face carries IP40 protection, so it's splash-resistant but not sealed; keep it inside a panel, not out in a washdown zone. Rated insulation voltage is 800 V, and it lives in an operating range of -25 °C to 70 °C. Storage range is wider: -40 °C to 80 °C, which matters if you're warehousing spares in an unheated building.