What this MCCB is and what it does
The Siemens SENTRON 3VA1112-4EF32-0BH0 is a 3-pole molded case circuit breaker (MCCB) designed for line protection in distribution panels. It carries a continuous current rating of 125 A at 40 °C, with thermal derating to 114 A at 70 °C, so the full 125 A is available at typical panel ambient temperatures below 55 °C. The interrupting capacity reaches 121 kA at 240 V AC and 75.6 kA at 415 V AC, giving substantial fault-clearing headroom for high-available-fault-current installations like transformer secondaries or large motor control centers. Rated insulation voltage is 800 V, which covers 480/600 V class systems with margin. The breaker ships with an integrated undervoltage release (UVR) and a factory-fitted auxiliary switch block: 2 auxiliary switches plus 1 trip alarm switch (HQ configuration). That means it can signal its status to a PLC or annunciator without a separate add-on module.
Panel fit and integration notes
The breaker occupies a 76.2 mm wide by 130 mm tall by 70 mm deep footprint — a standard 3-pole MCCB width for this current class. It mounts on a DIN rail or directly to a backplate via the screw terminals. The UVR coil draws its signal from the line side; verify the control voltage matches the panel's auxiliary supply before commissioning. Maximum power loss at rated current is 30.6 W, so account for that heat in a sealed enclosure's thermal calculation.