The Siemens SENTRON 3VA1225-4EF42-0CC0 is a 4-pole molded case circuit breaker (MCCB) rated for a continuous current Iu of 250 A, configured for line protection with a TM240 thermal-magnetic release. It carries an undervoltage release (UVR) and two auxiliary switches (HQ type) integrated at the factory — no field retrofit needed for those functions.
Breaking capacity and selectivity headroom
The interrupting ratings climb steeply with voltage: 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 figure at 240 V gives real headroom for high-fault installations like transformer secondaries or large motor control centers — you can coordinate downstream without worrying about the main breaker clearing first.
Thermal derating — the real-world current
The 250 A rating holds flat from 40 °C through 50 °C. Above that it steps down: 243.3 A at 55 °C, 236.5 A at 60 °C, 229 A at 65 °C, and 223 A at 70 °C. If your panel ambient runs hot — say a packed enclosure near a furnace line — the 70 °C figure is the one to size against. The TM240 release is calibrated for this curve; no separate derating factor to calculate.
Panel fit and auxiliary wiring
Dimensions are 140 mm wide, 158 mm high, 70 mm deep — a standard SENTRON 3VA frame that mounts on a DIN rail or panel plate. The two factory-fitted auxiliary switches (HQ) share the same housing; no add-on module needed for status feedback. The undervoltage release is wired separately — verify polarity on the coil before energizing. Front protection is IP40, so keep it inside a closed enclosure.