What it is and what it does
The Siemens 3VA1112-4EE46-0AA0 is a 4-pole SENTRON molded case circuit breaker (MCCB) rated for line protection. It carries 125 A continuously at 40 °C ambient, with a TM220 thermal-magnetic trip unit that handles overloads and short circuits in one package — no separate relay needed. The 121 kA breaking capacity at 240 V AC means it can safely interrupt a fault up to that level without the arc flashing over to adjacent gear; that kind of headroom is what you spec when the utility transformer is close and the available fault current is high.
Ratings and what they mean for fit
The 125 A rating holds from 40 °C through 50 °C without derating — that's a solid thermal margin for a warm panel. At 55 °C it's 122 A, at 60 °C it's 120 A, and at 70 °C it's 114 A. The breaking capacity drops as voltage rises: 75.6 kA at 415 V, 52.5 kA at 440 V, and 11.9 kA at 500 V and 690 V. The rated insulation voltage is 800 V, so the breaker's internal clearance is designed for 690 V systems. Front IP40 keeps dust out of the mechanism; the rest of the body is open to the enclosure air for heat shedding.
Panel fit and integration
Dimensions are 130 mm high, 101.6 mm wide, 70 mm deep — a 4-pole MCCB that fits a standard panel footprint. No undervoltage release, no shunt trip, no communication module on this variant; it's a straight thermal-magnetic breaker for distribution. Power loss is 28.1 W maximum at rated load, so account for that heat in the enclosure sizing. Storage range is -40 °C to 80 °C; operating range is -25 °C to 70 °C.