What this MCCB is and what it does
The Siemens 3VA1225-5EF32-0AC0 is a SENTRON molded case circuit breaker (MCCB) designed for line protection in industrial distribution panels. It carries a 250 A continuous rating at ambient temperatures up to 50 °C without derating, then steps down to 243 A at 55 °C, 237 A at 60 °C, 230 A at 65 °C, and 223 A at 70 °C — the thermal curve matters if this breaker sits next to other heat sources in a crowded enclosure. The TM240 overcurrent release is a thermal-magnetic type, meaning it uses a bimetal strip for overload protection and a solenoid for short-circuit response. No ground-fault monitoring, no undervoltage release, no communication function — this is a straight feeder or branch breaker, not a smart device.
Breaking capacity — what the numbers mean for fault duty
Rated breaking capacity varies sharply with system voltage: 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. The 187 kA figure at 240 V is high — this breaker can clear a massive fault on a low-voltage secondary without upstream fuses needing to coordinate. At 690 V the 17 kA is more modest; check the available fault current at your transformer secondary before committing the BOM line.
Physical fit and panel integration
Three-pole construction, 105 mm wide, 158 mm tall, 70 mm deep — standard MCCB footprint for a 250 A frame. The 70 mm depth means it clears most 200 mm deep enclosures with room for rear-mounted busbars. Rated insulation voltage is 800 V, so it can sit on a 690 V bus without derating the dielectric.