250 A MCCB with undervoltage release — current-production SENTRON
The Siemens 3VA1225-6GF42-0BA0 is a SENTRON molded case circuit breaker rated 250 A continuous, 4-pole, with a TM240 thermal-magnetic release and an integrated undervoltage release (UVR). It is designed for line protection in distribution panels and switchboards. The interrupting capacity is voltage-dependent: 220 kA at 240 V, 154 kA at 415 V, 75.6 kA at 440 V, 30 kA at 500 V, and 17 kA at 690 V. That means at 415 V it clears a 154 kA fault without cascading upstream — a high-fault rating for a 250 A frame. Rated insulation voltage is 800 V, so it can be applied in 690 V systems with margin on the insulation coordination.
Thermal derating and panel fit
The breaker carries 250 A continuously up to 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. If the panel ambient runs 60 °C, plan for 237 A max — the full 250 A is not available. Dimensions are 140 mm wide, 158 mm high, 70 mm deep — a standard 4-pole MCCB footprint for DIN-rail or panel-mount integration. The 70 mm depth leaves clearance for rear-connected busbars in a typical 200 mm deep enclosure. Maximum power loss is 59.5 W at rated current. Factor that into the enclosure thermal budget — at 250 A the breaker dissipates nearly 60 W, which adds to the internal temperature rise.
Lifecycle and sourcing
The TM240 release is a thermal-magnetic type, not electronic. No communication function, no ground-fault monitoring. If your BOM requires a communicating breaker or GF protection, this is not the variant.