What this MCCB does and where it fits
The Siemens 3VA1225-6EF42-0KH0 is a SENTRON molded case circuit breaker (MCCB) rated for line protection — it sits in a distribution panel or switchboard as the main feeder or large-branch protection on a 4-wire system. The 250 A continuous rating (Iu) holds at ambient temperatures up to 50 °C without derating; at 55 °C it still carries 243.3 A, and at 70 °C it's good for 223 A. That thermal curve means you can run it in a hot enclosure and still get nearly full rated current. Breaking capacity is the headline number here: 220 kA at 240 V, 154 kA at 415 V, 36 kA at 440 V, and 17 kA at 690 V. That's a high-interrupting rating — it clears a bolted fault without the arc flash escalating upstream. The 4-pole version handles three-phase plus neutral, and the IP40 front protection keeps dust and small tools out of the breaker face in a clean panel environment.
What the ratings mean for your panel
The 3VA1225-6EF42-0KH0 measures 70 mm deep, 140 mm wide, and 158 mm tall. That depth is shallow enough for a standard 200 mm deep enclosure — you won't need a deep can. The width of 140 mm for a 4-pole 250 A MCCB is typical; plan for a 4-module-wide cutout in the mounting plate. The overcurrent release is a TM240 thermal-magnetic unit, so it's a fixed-trip breaker — no interchangeable rating plugs. The shunt trip (STL) is integrated, and the auxiliary contact block is a 2-aux + 1-trip-alarm switch (HQ).