What the interrupting ratings mean for your panel
The Siemens SENTRON 3VM1112-4EE36-0AA2 is a 3-pole molded case circuit breaker (MCCB) from the 3VM1 IEC frame, sized for 125 A continuous duty. What sets this unit apart is its breaking capacity class S: it clears 121 kA at 240 V AC and 76 kA at 415 V AC. That 76 kA figure at 415 V is the one that governs most industrial panel coordination studies — it tells you this breaker can interrupt a fault up to that level without upstream devices needing to trip, which keeps selectivity intact on a distribution board feeding motor control centers or downstream subpanels. The TM220 overcurrent release provides LI protection (long-time and instantaneous), with overload protection Ir adjustable from 88 A to 125 A and short-circuit protection Ii fixed at 10 x In. That means you set the thermal pickup to match your load cable or transformer feeder, and the magnetic trip holds at 1250 A — no ground-fault module here, so this is a straight line-protection breaker for feeders or main incomers where GFCI is handled downstream.
Thermal derating and enclosure fit
Rated continuous current holds at 125 A from 40 °C through 50 °C ambient, then derates to 122 A at 55 °C and 120 A at 60 °C. That 5 °C window between 50 °C and 55 °C is where a panel builder needs to check the internal enclosure temperature — if your cabinet runs hot from drives or transformers, the 3 A drop at 55 °C is small but real. At 70 °C it still carries 114 A, which is better than many MCCBs in this frame class. Front-connected box terminals on the main circuit, IP40 protection on the front face. That IP40 is typical for switchboard mounting — it keeps tools and fingers out but isn't rated for washdown. Storage range spans -40 °C to 80 °C, so it can sit in an unheated warehouse or desert container without issue.