What this 250 A MCCB does on your line
The Siemens SENTRON 3VA1225-5GF42-0HH0 is a 4-pole molded case circuit breaker rated for 250 A continuous — no derating needed up to 50 °C, then it steps down to 243 A at 55 °C, 237 A at 60 °C, 230 A at 65 °C, and 223 A at 70 °C. That thermal curve matters if this breaker lives in a hot panel next to drives or transformers; at 70 °C you lose about 11% of the headroom. Interrupting capacity is 187 kA at 240 V, 121 kA at 415 V, 75.6 kA at 440 V, 30 kA at 500 V, and 17 kA at 690 V. That 187 kA at 240 V is the headline number — it tells you this breaker can clear a bolted fault on a high-capacity transformer secondary without welding its contacts shut. Rated insulation voltage is 800 V, so it's comfortable on 480/277 V and 600 V panels. It ships with a shunt trip (STL) for remote opening, plus two auxiliary switches and one trip alarm switch (HQ). The supplied basic switch is order code 3VA12255GF420AA0. No undervoltage release, no ground-fault monitoring, no communication module — this is a straightforward line-protection breaker with remote-trip capability.
Panel fit and integration
Dimensions: 158 mm high, 140 mm wide, 70 mm deep. That 70 mm depth is the body only — account for the shunt trip and auxiliary switch protrusion on the side. Mounts on a DIN rail or direct panel-mount; the 4-pole footprint matches standard Siemens SENTRON 3VA cutouts. Power loss at full load is 57 W — plan ventilation if the panel is sealed.