MCCB with 125 A continuous rating and 121 kA interrupting capacity
The Siemens 3VA1112-4EF36-0AD0 is a SENTRON molded case circuit breaker rated for 125 A continuous current at 40 °C, with a TM240 thermal-magnetic release and three poles. Its interrupting capacity reaches 121 kA at 240 V and 75.6 kA at 415 V — enough for high-fault utility feeds or transformer secondaries where the available short-circuit current is substantial. The 800 V rated insulation voltage (Ui) covers 480 V and 600 V class systems with margin. Three auxiliary switches (HQ type) are built in, so you get status feedback without adding a separate aux block. The front panel carries IP40 protection — fine for a clean indoor panel, not for washdown zones.
Current derating and thermal performance
The 125 A rating holds flat from 40 °C to 50 °C. Above that, it derates stepwise: 120 A at 55 °C, 117.5 A at 60 °C, 115 A at 65 °C, and 112.5 A at 70 °C. In a crowded panel with ambient near 60 °C, you lose about 6 % of the nominal current — plan the load accordingly. Storage range spans -40 °C to 80 °C; operating ambient goes -25 °C to 70 °C. The 15 000 mechanical endurance cycles are typical for a fixed-mounted MCCB of this class.
Physical fit and panel integration
The breaker measures 130 mm tall, 76.2 mm wide, and 70 mm deep. Depth of 70 mm leaves clearance for rear bus connections in a standard distribution panel.