What it is and what it does
The Siemens 3VA1225-5EF32-0AF0 is a SENTRON molded case circuit breaker (MCCB) rated for line protection in 3-pole configuration. It carries a continuous current rating of 250 A (Iu) and uses a TM240 thermal-magnetic trip unit — the thermal element handles overloads, the magnetic element clears short-circuits. Breaking capacity ranges from 187 kA at 240 V down to 17 kA at 690 V, so it can sit on the main feeder of a panel with high available fault current and still coordinate downstream.
Thermal derating and ambient limits
The breaker holds its full 250 A rating up to 50 °C ambient. Above that it derates linearly to 223 A at 70 °C. Operating range is -25 °C to +70 °C; storage range is -40 °C to +80 °C. If the panel runs hot — near a transformer or in a non-conditioned enclosure — the 55 °C to 70 °C derating curve is the one that governs real-world ampacity, not the nameplate 250 A.
Physical fit and auxiliary contacts
Dimensions are 105 mm wide, 158 mm high, 70 mm deep — a standard MCCB footprint for 250 A frame size. The front face carries IP40 protection. It ships with one auxiliary switch and one trip alarm switch (HQ configuration), which is enough for status feedback to a PLC or a remote annunciator without adding a separate accessory block.