What this MCCB is and what it does
The Siemens 3VA1112-5ED36-0AA0 is a SENTRON molded case circuit breaker (MCCB) designed for line protection in distribution panels. It carries a continuous current rating of 125 A at 40 °C, with a TM210 thermal-magnetic trip unit — meaning the thermal element handles overloads and the magnetic element clears short-circuits. The interrupting capacity hits 187 kA at 240 V, 121 kA at 415 V, and 75.6 kA at 440 V, so it can handle high-fault scenarios downstream of a large transformer without cascading upstream.
Ratings that drive the fit
The 125 A rating holds flat from 40 °C through 50 °C, then derates to 122 A at 55 °C, 120 A at 60 °C, 117 A at 65 °C, and 114 A at 70 °C. If your panel ambient runs above 50 °C, you lose about 3–5 A per 5 °C step — factor that into your load calc. The 3-pole design covers three-phase circuits; there's no undervoltage release or ground-fault monitoring built in, so those functions need external modules if required.
Panel integration and footprint
Mounts on a DIN rail or panel-mount base. Dimensions are 130 mm height, 76.2 mm width (3 inches), and 70 mm depth — a standard 3-pole MCCB footprint that fits most SENTRON distribution boards. IP40 on the front means it's protected against tools and small wires but not washdown; keep it inside a closed enclosure. Power loss at rated load is 28.1 W maximum, so ventilation matters if you're packing several breakers in a small cabinet.