What this MCCB is and where it fits
The Siemens 3VA2225-5HN42-0KB0 is a SENTRON 3VA2 molded case circuit breaker (MCCB) in the line protection version, rated for a continuous current Iu of 250 A across four poles. It carries an ETU350 electronic trip unit, which gives you adjustable long-time, short-time, and instantaneous protection curves — not a fixed thermal-magnetic. The 4-pole design with adjustable N-conductor protection (OFF, 50%, 100%) makes it a fit for 3-phase + neutral systems where you need to protect or not protect the neutral leg depending on the load balance. Breaking capacity is the headline: 187 kA at 240 V AC, 121 kA at 415 V and 440 V, 76 kA at 500 V, and 4.5 kA at 690 V. That 187 kA figure at 240 V means this breaker handles high-fault-current scenarios common in North American 240/120 V split-phase or 240 V delta services without needing a current-limiting fuse upstream. At 415/440 V — typical European industrial voltages — the 121 kA rating still covers most utility transformer secondary faults. The drop to 4.5 kA at 690 V tells you this is not the breaker for 690 V high-fault installations; for those, step up to the 3VA2 high-capacity variant.
Thermal derating and panel integration
Rated 250 A continuous up to 50 °C ambient. Above that, derate linearly: 241 A at 55 °C, 232 A at 60 °C, 222 A at 65 °C, 213 A at 70 °C. If your panel ambient runs 60 °C, you lose 18 A of headroom — factor that into the load schedule. The 86 mm depth, 140 mm width, and 181 mm height fit the standard 3VA2 cutout; no special adapter plate needed for most enclosure backpanels. IP40 on the front means it's protected against tools and wires >1 mm, but not against water ingress — keep it inside a sealed enclosure in washdown areas. Maximum power loss is 48 W. That's the heat you need to vent inside the enclosure. For a panel with multiple breakers at full load, sum the losses and size the ventilation or air conditioning accordingly — 48 W per breaker adds up fast in a multi-feeder lineup.