What it is and what it does
The Siemens 3VA1225-4GF42-0HA0 is a SENTRON molded case circuit breaker (MCCB) rated for 250 A continuous current, 4-pole, in a line protection configuration. It carries a TM240 thermal-magnetic overcurrent release — the 240 in the trip-unit designation refers to the thermal pickup range, not the frame size. The interrupting ratings are what drive the panel coordination: 121 kA at 240 V, 75.6 kA at 415 V, 25 kA at 440 V, and 11.9 kA at 690 V. That 121 kA at 240 V is the headline number for high-fault commercial services; the 75.6 kA at 415 V is the one that matters for most industrial 400 V distribution.
Thermal derating and panel integration
This breaker holds its full 250 A rating up to 50 °C ambient. Above that it derates: 243.3 A at 55 °C, 236.5 A at 60 °C, 229 A at 65 °C, and 223 A at 70 °C. If the panel ambient runs hot — say a sealed enclosure with drives below — you need to account for that curve at the busbar sizing step. The dimensions are 158 mm high, 140 mm wide, 70 mm deep. Front protection is IP40, so it's fine for a clean panel interior but not for washdown zones. The shunt trip (order code 3VA9688-0BL30) is integrated; no separate auxiliary contact version is fitted.