What the 250 A continuous rating means for your panel
The Siemens 3VA1225-4EF32-0DC0 is a SENTRON molded case circuit breaker (MCCB) rated for 250 A continuous current — that's the Iu figure that governs the main bus or feeder it protects, not a peak or short-time rating. At 40 °C ambient, it carries the full 250 A without derating; the curve holds flat through 50 °C, then drops to 243.3 A at 55 °C, 236.5 A at 60 °C, 229 A at 65 °C, and 223 A at 70 °C. For a mill panel near a furnace or drive cabinet pulling ambient above 50 °C, that thermal headroom matters — you size the breaker for the load at actual cabinet temperature, not the nameplate number. Breaking capacity is the other number that decides whether this breaker holds or vents on a fault. At 240 V it interrupts 121 kA; at 415 V, 75.6 kA; at 440 V, 25 kA; at 690 V, 11.9 kA. For a 480 V distribution panel in a steel mill, the relevant figure is the 415 V rating (75.6 kA) — that's the SCCR headroom you compare against the available fault current at the panelboard. If your upstream transformer can deliver 65 kA at the bus, this breaker clears it with margin. The overcurrent release is a TM240 thermal-magnetic type — fixed thermal trip for overload, magnetic instantaneous for short-circuit. No electronic adjustment, no communication module, no ground-fault monitoring. This is a line-protection version: it protects cable and bus from overload and short, not a motor or a downstream device with specific coordination curves. The auxiliary contacts are two HQ switches (form C), and there's an undervoltage release (UVR) integrated — if the control voltage drops, the breaker trips. That UVR is a separate order: 3VA9608-0BB25.
Panel fit and mounting — what the dimensions tell you
The 3VA1225-4EF32-0DC0 measures 158 mm high, 105 mm wide, and 70 mm deep. That 105 mm width is the critical dimension for a 3-pole MCCB in a multi-breaker lineup — it determines how many poles fit across a standard 600 mm panel section (five, with some wiring space). The 70 mm depth means it clears most shallow backpan enclosures without a sub-panel extension. IP40 on the front keeps dust out of the mechanism; the rest of the breaker is ventilated for thermal performance, so don't seal it inside a closed box without checking the temperature derate curve above.