What it is and what the ratings mean
The Siemens 3VA1112-5FE42-0AA0 is a SENTRON molded case circuit breaker (MCCB) with four poles, rated for a continuous current of 125 A at 40 °C and fitted with a TM220 thermal-magnetic overcurrent release. The TM220 designation means the thermal trip is fixed at 125 A (the frame rating), while the magnetic short-circuit pickup is adjustable — a common choice for feeder protection where you want the thermal element sized to the cable but some flexibility on the instantaneous trip threshold. Breaking capacity is the headline here: 187 kA at 240 V AC, 121 kA at 415 V, 76 kA at 440 V, and 17 kA at both 500 V and 690 V. That 187 kA at 240 V puts it in the high-interrupting category — it will clear a bolted fault on a large secondary transformer or a high-capacity bus without the arc flashing over. At 690 V the 17 kA figure is still respectable for most industrial motor-control centers, but you would check the available fault current at the panelboard before committing the BOM line. The part is rated for line protection (feeder duty), not motor protection — no separate overload relay class or ambient-compensated curve. If you need motor branch-circuit protection, you would pair this with a separate overload relay or look at the 3VA motor-protective versions with electronic releases.
Thermal derating and panel integration
Rated 125 A at 40 °C through 50 °C, then it derates: 122 A at 55 °C, 120 A at 60 °C, 117 A at 65 °C, 114 A at 70 °C. In a sealed, uncooled enclosure at 60 °C ambient you lose 5 A — not a showstopper, but if the design load is 125 A continuous, you need to either ventilate the panel or uprate to the next frame. The IP40 front protection means the breaker face is protected against tools and small wires, but the enclosure itself must handle the rest; no washdown rating here. Physical footprint: 130 mm high, 101.6 mm wide, 70 mm deep. Four-pole width is about 4 inches.
Lifecycle and sourcing posture
Lifecycle stage is current — Siemens still builds this order code. No NRND flag or phase-out notice in the evidence.