What this 320 A MCCB is and where it fits
The Siemens SENTRON 3VA1332-7GF42-0AA0 is a 4-pole molded case circuit breaker rated for 320 A continuous current at 40 °C, with a TM240 thermal-magnetic overcurrent release. It carries a 440 kA breaking capacity at 240 V, which drops to 242 kA at 415 V and 440 V, and 154 kA at 500 V — still 17 kA at 690 V. That SCCR headroom means it can be placed upstream of distribution panels without worrying about cascading faults, even on high-fault utility feeds. The IP40 front protection keeps dust out of the panel face, but the breaker is designed for enclosed mounting in a switchboard or enclosure, not standalone outdoor use.
Thermal derating and real-world loading
The 320 A rating holds flat from 40 °C to 50 °C. Above that, it derates linearly: 313 A at 55 °C, 306 A at 60 °C, 299 A at 65 °C, and 292 A at 70 °C. If the panel ambient runs warm — say, a packed enclosure near a furnace line — that 292 A at 70 °C is the number to design to, not the catalog 320 A. The maximum operating temperature is 70 °C, with storage from -40 °C to 80 °C. Power loss at full load hits 80.1 W, which adds to the enclosure heat budget.
Integration notes for the panel builder
The breaker measures 248 mm high, 184 mm wide, and 110 mm deep. That 110 mm depth is the dimension to watch when spacing the backplate from the enclosure door — it dictates the minimum clearance for the arc chamber and line-side lugs. The 184 mm width for a 4-pole frame is standard for this class; it occupies roughly 7.24 inches of DIN-rail or mounting-plate width. The TM240 release is non-interchangeable in the field, so verify the trip curve against your load before mounting. A motor drive option is available as a factory or field accessory, which allows remote open/close without opening the door.