Rating and trip unit — what drives the BOM decision
The Siemens 3VA2225-5HM42-0DF0 is a 4-pole SENTRON molded case circuit breaker rated 250 A continuous at 40 °C through 50 °C, with a slight thermal derating curve beginning at 55 °C (241 A) and stepping down to 213 A at 70 °C. The ETU330 electronic trip unit handles the overcurrent protection logic. It is a line-protection variant, meaning it is configured for feeder and distribution duty rather than motor or generator protection — the trip curves and time-delay settings are tailored for cable and busbar protection in a main or sub-distribution panel. Breaking capacity is substantial: 187 kA at 240 V, 121 kA at 415 V and 440 V, 75.6 kA at 500 V, and 4.5 kA at 690 V.
The undervoltage release is present, so the breaker can be shunt-tripped via a separate control voltage for emergency-stop or undervoltage protection schemes.