What this MCCB carries and where it fits
The Siemens SENTRON 3VA1112-4EF32-0JH0 is a 3-pole molded case circuit breaker rated 125 A continuous at 40 °C, with an interrupting capacity of 121 kA at 240 V AC. That interrupting figure drops to 75.6 kA at 415 V and 52.5 kA at 440 V — still enough headroom for most industrial service-entrance or feeder applications where fault current runs high. Rated insulation voltage is 800 V, so it handles 480Y/277 V and 600 V delta systems without derating the dielectric. The 70 mm depth and 76.2 mm width mean it fits standard SENTRON panel cutouts; if you're swapping an older 3VA1 frame, the footprint matches.
Thermal derating and power loss
Continuous current holds at 125 A from 40 °C up to 50 °C, then steps down: 122 A at 55 °C, 120 A at 60 °C, 117 A at 65 °C, and 114 A at 70 °C. If the panel ambient runs hot — say a packed enclosure near a furnace line — that 114 A at 70 °C is the number to size against, not the 125 A nameplate. Maximum power loss is 28.1 W, which matters for enclosure heat rise calculations when grouping multiple breakers.
Built-in auxiliaries and release options
This variant ships with 2 auxiliary switches plus 1 trip alarm switch (HQ configuration), and a shunt trip release (STL) for remote tripping. No undervoltage release, no ground-fault monitoring, no communication module — it's a straight line-protection breaker with basic signaling. The shunt trip lets a safety PLC or E-stop circuit kill power without a separate contactor; just verify the STL coil voltage matches your control supply.