What this MCCB is and what the ratings mean for fit
The Siemens 3VA1125-5EF32-0KC0 is a SENTRON molded case circuit breaker (MCCB) configured for line protection — meaning it guards feeder and branch circuits against overload and short circuit, not motor or generator duty. It is a 3-pole unit rated at 25 A continuous current (Iu) and carries a TM240 thermal-magnetic release, so the thermal pickup tracks the cable temperature and the magnetic trip is fixed at 240 A for instantaneous short-circuit clearing. The interrupting ratings are the headline here: 187 kA at 240 V, 121 kA at 415 V, 75.6 kA at 440 V, and 17 kA at 690 V. That 187 kA at 240 V means this breaker can safely clear a fault current up to 187,000 A without welding its contacts or rupturing the case — critical for high-available-fault-current panels like transformer secondaries or large motor control centers. The 17 kA at 690 V is the ceiling for 690 V line-ups; if your system SCCR exceeds that at 690 V, you need a current-limiting upstream device or a higher-rated frame. Thermal derating is published: full 25 A up to 50 °C, then 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 breaker lives in a hot panel — say next to a drive or inside a sun-exposed enclosure — size the load at the ambient temperature it actually sees, not the 40 °C base.
Panel integration and auxiliary options
The 3VA1125-5EF32-0KC0 measures 76.2 mm wide, 130 mm tall, and 70 mm deep — a standard 3-pole MCCB footprint that fits most DIN-rail or screw-mount panel layouts. IP40 on the front means it is protected against tools and wires >1 mm, but not against water ingress; keep it inside a rated enclosure. It ships with 2 auxiliary switches (HQ type) built in, plus a shunt trip (STL) release for remote tripping. The integrated auxiliary trip order code is 3VA9688-0BL33 if you need a spare or replacement. No undervoltage release, no ground-fault monitoring, no communication module — this is a basic line-protection breaker, not a smart or selective device.