What this MCCB carries
The Siemens 3VA1225-4EF42-0BH0 is a SENTRON molded case circuit breaker (MCCB) rated for 250 A continuous current at 40 °C, with a 4-pole configuration and a TM240 thermal-magnetic release. It's the line-protection variant — meaning it's built for feeder and main breaker duty, not motor branch circuit protection. Breaking capacity is the headline here: 121 kA at 240 V AC, 75.6 kA at 415 V, 25 kA at 440 V, and 11.9 kA at 690 V. That 121 kA figure at 240 V is enough for high-fault utility transformer secondaries or large bus risers where the available fault current is substantial. The 75.6 kA at 415 V covers most European industrial distribution panels without needing a current-limiting upstream device. Rated insulation voltage is 800 V, so it's comfortable in 690 V systems with margin. The TM240 release gives a fixed thermal pickup at 250 A (the rated current) and a magnetic trip that's adjustable via the front dial — typical for coordinating with downstream breakers on a selective scheme.
Fit and panel integration
Dimensions are 158 mm height, 140 mm width, 70 mm depth. Front face carries IP40 protection — fine for a clean indoor panel, but not rated for washdown or outdoor exposure. The auxiliary contact block is a 2 NO/NC plus one separate trip-alarm switch (HQ type), which gives a dedicated signal for remote fault indication without sharing the auxiliary contact set. An undervoltage release (UVR) is built in — part of the order code's design. That means the breaker will trip if control voltage drops below the release's dropout threshold, which is standard for applications where loss of control power must automatically disconnect the load (e.g., emergency stop circuits or interlocked machine zones). The UVR is designated as 3VA9608-0BB11.
Thermal derating and operating range
The breaker holds its full 250 A rating up to 50 °C ambient. Above that it derates linearly: 243.3 A at 55 °C, 236.5 A at 60 °C, 229 A at 65 °C, and 223 A at 70 °C. If your panel internal ambient runs hot — say a packed enclosure with drives — you'll need to account for that derating at the design stage. Operating range is -25 °C to +70 °C; storage range is -40 °C to +80 °C. Mechanical endurance is rated at 15,000 operations.