What this MCCB is and what the ratings mean
The SENTRON 3VM1112-3GE42-0AA0 is a 4-pole molded case circuit breaker (MCCB) designed for line protection in distribution panels. Its TM220 thermal-magnetic release provides fixed overload and short-circuit protection curves — no interchangeable trip units, so the trip setting is locked at the factory. Rated 125 A continuous at 40 °C, it holds that current flat through 50 °C (125 A at 50 °C), then derates linearly to 114 A at 70 °C. That thermal stability means you don't lose headroom in a warm enclosure until you're well above typical panel ambient. Breaking capacity is the real selector here: 76 kA at 240 V AC, 53 kA at 415 V AC, 32 kA at 440 V AC, and 12 kA at 500 V AC. At 415 V — common for European industrial distribution — the 53 kA figure puts it in the high-fault tier for a 125 A frame. That means it can interrupt a bolted fault up to 53 kA without upstream fuses needing to clear first, which simplifies coordination studies. Rated insulation voltage is 800 V, so the 500 V AC breaking capacity is within the insulation envelope. The front face carries IP40 protection — splash-proof from the front but not sealed for washdown; mount it inside a panel with a door. No trip indicator, no undervoltage release, no communication module — this is a straight electromechanical breaker, no auxiliary electronics to fail.
Sourcing and lifecycle
Maximum power loss is 23 W — that's the heat it dumps into the enclosure at full rated current. For a panel designer, that's the number to plug into the thermal rise calculation. If you're retrofitting this into an existing panel that ran cooler, verify the enclosure's dissipation capacity doesn't exceed the rated rise.
Physical fit and panel integration
Dimensions: 70 mm deep, 101.6 mm wide (4 inches), 130 mm high (5.12 inches). The 4-pole width at 101.6 mm is the standard 4-inch MCCB footprint for this class — it fits Siemens SENTRON mounting bases and most DIN-rail adapters for 4-pole frames. Depth of 70 mm means it clears a standard 200 mm deep enclosure with room for rear-connected busbars. The N-conductor protection is rated at 100% — meaning the neutral pole is fully rated, not reduced. That matters for 4-wire systems where the neutral carries phase imbalance current. No ground-fault monitoring version is fitted, so this is a straight overcurrent-only device.