What this MCCB carries and where it fits
The Siemens 3VA1112-5EF32-0JC0 is a 3-pole SENTRON molded case circuit breaker rated for 125 A continuous current (Iu) with a TM240 thermal-magnetic overcurrent release. It is configured as a line-protection device — meaning it guards feeder and distribution circuits against overload and short-circuit, not motor or generator protection. The 187 kA breaking capacity at 240 V and 121 kA at 415 V put it in the high-interrupting class for industrial switchboards where available fault current is substantial. The 800 V rated insulation voltage (Ui) covers 480 V and 600 V class systems with headroom. The shunt trip (STL) release allows remote tripping via a control signal — useful for emergency-stop or supervisory shutdown circuits. Two HQ auxiliary switches (form C) are integrated for status feedback to a PLC or annunciator panel. The TM240 release is a fixed thermal-magnetic unit; no interchangeable trip units here, so the overload setting is factory-set and not field-adjustable.
Thermal derating and panel fit
The 125 A rating holds from 40 °C through 50 °C ambient. Above that it derates linearly: 120 A at 55 °C, 117.5 A at 60 °C, 115 A at 65 °C, and 112.5 A at 70 °C. If this breaker sits in a warm enclosure — say, above a drive or near a transformer bank — use the 55 °C or 60 °C column for your continuous load calculation. The 70 mm depth and 76.2 mm width match the standard SENTRON 3VA mounting footprint; it bolts into the same busbar and lug kit as other 125 A frames in the family. IP40 on the front face means it is protected against tools and wires >1 mm but not against dust ingress — keep the enclosure door closed.