MCCB with shunt trip for line protection
The Siemens SENTRON 3VA1225-4EF32-0JA0 is a 3-pole molded case circuit breaker (MCCB) rated for 250 A continuous current, configured for line protection with a TM240 thermal-magnetic overcurrent release. It includes a factory-integrated shunt trip (STL) release for remote tripping, making it suitable for applications where emergency-off or supervisory control signals must open the breaker independently of the overcurrent mechanism. Breaking capacity is rated at 121 kA at 240 V, 75.6 kA at 415 V, 25 kA at 440 V, and 11.9 kA at 690 V — figures that cover most industrial distribution panels up to 690 V line-to-line. The 250 A frame with TM240 release means the thermal pickup is fixed at 250 A; the magnetic trip threshold is set by the TM240 curve, which is sized for cable and busbar protection rather than motor overload duty. Dimensions are 105 mm wide, 158 mm high, and 70 mm deep — a standard 3-pole SENTRON 3VA frame that fits the same panel cutout and busbar spacing as other 3VA breakers in this current class. Front protection is IP40, adequate for enclosed distribution boards where the breaker face is behind a door.
Thermal derating and ambient limits
The 250 A rating holds continuously from 40 °C through 50 °C ambient. Above that, derating applies: 243.3 A at 55 °C, 236.5 A at 60 °C, 229 A at 65 °C, and 223 A at 70 °C. Operating ambient range is -25 °C to +70 °C; storage range is -40 °C to +80 °C. For a panel near a tire-curing press or other heat source, the 55 °C derated figure is the one to size against.
Integrated shunt trip and subcomponents
The shunt trip release (STL) is designed as an auxiliary release — part number 3VA9688-0BL32 is the integrated trip unit. The supplied basic switch is 3VA12254EF320AA0. There is no undervoltage release, no auxiliary contact version, no ground-fault monitoring, no communication function, and no phase-failure detection on this variant. The trip indicator is also absent, so visual status is limited to the handle position.