What the ratings mean for your panel
The Siemens SENTRON 3VA1112-4EF32-0HA0 is a 3-pole molded case circuit breaker (MCCB) rated for 125 A continuous current at 40 °C, with no derating needed up to 50 °C — it holds the full 125 A through that range. Above 50 °C it steps down: 120 A at 55 °C, 117.5 A at 60 °C, 115 A at 65 °C, and 112.5 A at 70 °C. That thermal curve means a panel running at 50 °C ambient gets the full nameplate; above that, the breaker self-limits to stay within its insulation temperature class. Breaking capacity is given at four voltages: 121 kA at 240 V, 75.6 kA at 415 V, 52.5 kA at 440 V, and 11.9 kA at 690 V. For a 400 V distribution panel the 75.6 kA figure governs — that is the fault current the breaker can interrupt without welding its contacts or cascading upstream. The 690 V rating (11.9 kA) is lower because arc extinction gets harder as voltage rises; if your system runs at 690 V, verify that the available fault current stays under that threshold. The overcurrent release is a TM240 — thermal-magnetic, fixed at 240 A short-circuit pickup. This is a line-protection variant (not feeder or generator protection), so it is intended for branch-circuit or main-switch duty where the load is a distribution bus or a group of downstream breakers. The insulation voltage is rated 800 V, giving headroom for 690 V systems.
Integration and mounting
The breaker measures 130 mm high, 76.2 mm wide, and 70 mm deep. It mounts on a DIN rail or directly to a panel backplate via the screw terminals. The front face carries IP40 protection — splash-proof behind a panel door but not washdown-rated. No auxiliary contacts are fitted (the auxiliary contact version is listed as "Without"), so if you need remote status or alarm signaling, you will add an external aux switch or a shunt trip (the integrated auxiliary trip is order code 3VA9688-0BL30). A shunt trip release is designed into the breaker (listed as "Shunt trip (STL)"), but there is no undervoltage release, no ground-fault monitoring, and no communication function. This is a plain line-protection MCCB — no Modbus, no phase-failure detection, no integrated metering. For a panel that needs remote trip or status feedback, the shunt trip plus an external PLC digital input covers it.