What it is and what it does
The Siemens SENTRON 3VA1112-4EF32-0KA0 is a 3-pole molded case circuit breaker (MCCB) rated for line protection. It carries a continuous current of 125 A at 40 °C, with a thermal-magnetic overcurrent release (TM240) that handles overloads and short circuits without external power. The insulation voltage is rated 800 V, so it's comfortable on 400 V and 690 V distribution systems. Breaking capacity is 121 kA at 240 V, 75.6 kA at 415 V, and 52.5 kA at 440 V — enough to clear a bolted fault on most industrial secondary distribution without upstream coordination headaches. At 690 V it still holds 11.9 kA, which covers motor-circuit faults on 690 V drives.
Thermal derating and real-world current
The 125 A rating holds flat from 40 °C to 50 °C. Above that it starts to taper: 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 next to a drive cabinet or a transformer — size the load side for the derated figure, not the nameplate 125 A. Power loss at full rated current is 28.1 W maximum. That's the heat the breaker dumps into the enclosure; factor it into the panel's thermal budget, especially in a sealed box.
Auxiliary release and integration
This variant includes a shunt trip (STL) auxiliary release. That means you can trip the breaker remotely by applying a control voltage — useful for emergency-stop circuits or supervisory shutdowns. No undervoltage release on this order code, so if you need UVR for a safety circuit, this isn't the one. No communication module, no ground-fault monitoring, no trip indicator. It's a straight line-protection MCCB with remote trip capability. The basic switch assembly is order code 3VA11124EF320AA0.
Physical fit and environment
Dimensions: 130 mm high, 76.2 mm wide (3 inches), 70 mm deep. The 70 mm depth is the key number for panel depth clearance. Operating temperature range is -25 °C to 70 °C; storage goes from -40 °C to 80 °C. That covers unheated warehouses and outdoor cabinets in most climates.