What this MCCB delivers
The Siemens 3VA1125-5EF36-0KH0 is a SENTRON molded case circuit breaker (MCCB) rated for 25 A continuous current (Iu) at 40 °C through 50 °C, with a thermal-magnetic TM240 overcurrent release and a 3-pole configuration. Its interrupting capacity reaches 187 kA at 240 V, 121 kA at 415 V, and 75.6 kA at 440 V — enough to handle high-fault utility feeds or transformer secondaries without cascading upstream. The frame is sized for line protection, meaning it is set up for cable and busbar protection rather than motor or generator duty. It includes a shunt trip (STL) for remote opening and a 2-auxiliary + 1-trip-alarm switch (HQ) for status feedback to a PLC or annunciator panel.
Thermal derating and panel fit
The 25 A rating holds flat from 40 °C to 50 °C, then derates to 24 A at 55 °C, 23.5 A at 60 °C, 23 A at 65 °C, and 22.5 A at 70 °C. If the panel ambient runs above 50 °C, you need to account for that drop in the branch circuit load. The case dimensions — 70 mm deep, 76.2 mm wide, 130 mm high — fit the standard SENTRON 3VA mounting footprint, so it swaps into existing DIN-rail or screw-mount panels without re-drilling. Front IP40 protection keeps out tools and fingers; the enclosure itself is not sealed against washdown.