What this 4-pole MCCB carries
The Siemens 3VA1225-6EF42-0AA0 is a SENTRON molded case circuit breaker (MCCB) with four poles, rated 250 A continuous at 40 °C and designed for line protection. Its TM240 thermal-magnetic release handles overload and short-circuit tripping without an external control signal — no undervoltage release, no communication module, no ground-fault monitoring built in. That keeps the wiring simple: power in, power out, no aux connections to pull. The interrupting ratings climb as voltage drops: 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 220 kA figure at 240 V means it can clear a bolted fault on a large transformer secondary without the arc re-striking — useful for service-entrance or main-tie applications where available fault current is high.
Thermal derating — what the 250 A actually means in a warm panel
The 250 A rating holds flat from 40 °C to 50 °C. Above that the TM240 release starts pulling back: 243 A at 55 °C, 237 A at 60 °C, 230 A at 65 °C, and 223 A at 70 °C. If the breaker lives in a crowded enclosure with drives or transformers bleeding heat, the 70 °C figure (223 A) is the one to size against — the nameplate 250 A is only valid below 50 °C ambient. Dimensions are 158 mm tall, 140 mm wide, 70 mm deep. That 70 mm depth keeps the can from protruding too far past the DIN rail — useful when the gland plate is tight against the back wall. The front face carries IP40 protection, so it's fine in a clean panel but not rated for washdown areas.
Panel fit and mounting notes
Four-pole construction means it occupies the full width of a standard 140 mm slot in a distribution panel. The TM240 release is factory-set; no field-adjustable trip curves, so verify the 250 A continuous rating matches the downstream load before installation. Rated insulation voltage is 800 V, giving headroom for 480 V and 600 V systems without de-rating the insulation. Maximum power loss is 57 W at full load. In a sealed enclosure that heat has to be considered for the thermal budget — a 250 A breaker dumping 57 W into a small box can raise ambient enough to trigger the derating curve above.