125 A MCCB with TM220 release — panel selectivity and interrupting capacity
The Siemens SENTRON 3VA1112-4GE46-0AA0 is a 4-pole molded case circuit breaker rated 125 A continuous at 40 °C, with a TM220 thermal-magnetic trip unit. The interrupting capacity hits 121 kA at 240 V AC and 75.6 kA at 415 V AC, giving you headroom for high-fault utility feeds or transformer secondaries where a standard MCCB would cascade. Rated insulation voltage is 800 V, operating voltage 690 V AC — sized for 400/480 V distribution panels with room to spare. The 4-pole design with 100% N-conductor protection means it switches the neutral, not just monitors it, which matters for TN-S or IT systems where you need full isolation.
Current derating and thermal budget
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 this breaker sits in a crowded enclosure with other heat sources, the 28.1 W maximum power loss adds to the internal temperature rise — factor that into your panel thermal calculation, especially if ambient near the MCCB exceeds 50 °C. The IP40 front face keeps dust out of the enclosure cutout; no washdown rating here, so keep it inside a cabinet.
Dimensions and panel fit
The breaker measures 70 mm deep, 101.6 mm wide, and 130 mm tall. That 4-inch width (101.6 mm) is the standard 4-pole MCCB footprint — it fits Siemens 3VA panelboard cutouts and most DIN-rail adapter plates designed for the SENTRON series. No trip indicator, no undervoltage release, no communication module on this variant; it's a straight thermal-magnetic line-protection breaker with the TM220 curve.