The Siemens 3VA1225-4EE32-0AA0 is a SENTRON molded case circuit breaker (MCCB) rated for 250 A continuous at 40 °C, in a 3-pole configuration, designed specifically for line protection in distribution panels.
This breaker delivers 121 kA breaking capacity at 240 V AC, 75.6 kA at 415 V, 52.5 kA at 440 V, 17 kA at 500 V, and 11.9 kA at 690 V. For a panel builder, the 121 kA at 240 V means it can sit at the main service entrance on a 240 V delta system with a high available fault current — no need for a current-limiting fuse upstream. At 415 V, the 75.6 kA figure still covers most industrial transformer secondary faults. The 690 V rating (11.9 kA) is lower but still adequate for 690 V motor control centers where the transformer impedance limits fault current.
Thermal Derating — Don't Oversize the Panel
The 250 A rating holds flat from 40 °C through 50 °C ambient. Above that, it derates: 243 A at 55 °C, 237 A at 60 °C, 230 A at 65 °C, and 223 A at 70 °C. The 57 W maximum power loss at rated current means that heat has to be managed inside the enclosure; a 250 A breaker dumping 57 W into a small box will raise the internal temperature by several degrees, so factor that into your thermal simulation.
The breaker measures 105 mm wide, 158 mm high, and 70 mm deep. The 105 mm width for a 3-pole frame is standard for this class; it will fit Siemens 3VA mounting accessories and busbar systems.