250 A MCCB with TM240 release — what the ratings mean for your panel
The Siemens SENTRON 3VA1225-5GF42-0AA0 is a 4-pole molded case circuit breaker rated 250 A continuous, designed for line protection in distribution panels. The TM240 thermal-magnetic release means the thermal element is calibrated for a 240 A frame, with the magnetic trip set to handle inrush without nuisance tripping on motor or transformer starts. At 40 °C it carries the full 250 A; derate linearly to 223 A at 70 °C if the panel ambient runs hot. Breaking capacity is the number that decides whether this breaker clears a fault or welds shut. At 240 V it interrupts 187 kA — enough for a high-capacity transformer secondary. At 415 V it's 121 kA, at 440 V it drops to 75.6 kA, and at 690 V it's still 17 kA. That's a wide voltage band, so verify your system voltage against the curve before specifying. Rated insulation voltage is 800 V, so the breaker is suitable for 690 V line-to-line systems with margin. Front-side protection is IP40 — fine for a closed panel, not for washdown areas.
Panel fit — dimensions and integration
The 3VA1225-5GF42-0AA0 measures 158 mm high, 140 mm wide, and 70 mm deep. It is a 4-pole MCCB. Power loss is 57 W maximum at rated current. Factor that into your enclosure thermal calculation — in a sealed panel with multiple breakers, 57 W per pole assembly adds up. The storage temperature range of -40 °C to 80 °C covers most site conditions; operating range is -25 °C to 70 °C.