125 A MCCB with TM220 release — what the ratings mean for your panel
The Siemens 3VA1112-3GE46-0AA0 is a SENTRON molded case circuit breaker rated for 125 A continuous at 40 °C, with a TM220 thermal-magnetic overcurrent release — the thermal element handles overloads, the magnetic element handles short-circuits, and the 220 designation means the magnetic pickup is fixed at 10× In (1250 A). Breaking capacity is what decides whether this breaker clears a fault without welding its contacts or cascading upstream: 75.6 kA at 240 V, 52.5 kA at 415 V, 32 kA at 440 V, and 11.9 kA at both 500 V and 690 V. If your available fault current at the panel exceeds these numbers at the system voltage, you need a higher-rated frame or a current-limiting upstream device. 4-pole design suits line protection in three-phase systems where the neutral requires overcurrent protection or isolation.
Thermal derating and panel integration
The 125 A rating holds flat through 50 °C ambient; above that it derates to 122 A at 55 °C, 120 A at 60 °C, 117 A at 65 °C, and 114 A at 70 °C. If the breaker sits inside a crowded enclosure with poor airflow, use the 70 °C figure for your continuous load calculation — 114 A is the real limit, not the catalog 125 A. Dimensions are 130 mm height, 101.6 mm width, 70 mm depth — a standard 4-pole MCCB footprint that fits most DIN-rail or panel-mount enclosures. IP40 on the front means it's protected against tools and wires >1 mm, but not against water ingress; keep it inside a rated enclosure for washdown areas. Power loss is 28.1 W maximum.