What this MCCB is and where it fits
The Siemens 3VA1225-6EF42-0KA0 is a SENTRON molded case circuit breaker (MCCB) with a 250 A rated continuous current (Iu) and a TM240 thermal-magnetic overcurrent release. Four poles cover three-phase plus neutral, and the shunt trip (STL) allows remote tripping. Breaking capacity hits 220 kA at 240 V, 154 kA at 415 V, 36 kA at 440 V, and 17 kA at 690 V — so it handles high-fault utility feeds and transformer secondaries. The 70 mm depth and 140 mm width fit standard MCCB panel cutouts; front IP40 keeps dust out of the enclosure.
Current rating across the panel ambient range
The 250 A continuous rating holds flat from 40 °C up to 50 °C. At 55 °C it derates to 243.3 A, at 60 °C to 236.5 A, at 65 °C to 229 A, and at 70 °C to 223 A. If the panel ambient runs above 50 °C, size the load side accordingly — the breaker will carry less than the nameplate 250 A.