What this MCCB delivers — and what the ratings mean for your panel
The Siemens SENTRON 3VA1112-4EF32-0AF0 is a 3-pole molded case circuit breaker (MCCB) rated for line protection duty. It carries a continuous current of 125 A at 40 °C, and the thermal-magnetic release (TM240) handles overloads and short-circuits without an external trip unit. The interrupting capacity tells you where it can safely clear a fault: 121 kA at 240 VAC, 75.6 kA at 415 VAC, 52.5 kA at 440 VAC, and 11.9 kA at both 500 VAC and 690 VAC. That means in a 480 VAC panel — common across North American industrial plants — the breaker can interrupt over 50 kA of prospective fault current, which covers most secondary-side distribution scenarios without needing a current-limiting upstream device. The rated insulation voltage of 800 V gives headroom for 690 VAC systems, so it fits European 400 V and North American 480 V designs on the same frame.
Fit and footprint for panel integration
Dimensions are 130 mm height, 76.2 mm width, 70 mm depth. The 76.2 mm width is a standard 3-pole MCCB footprint. Depth of 70 mm leaves clearance behind the panel door for wiring space and auxiliary wiring. The auxiliary switch configuration comes factory-fitted: one auxiliary switch plus one trip alarm switch (HQ type). Maximum power loss is 28.1 W.
Thermal derating and operating range
The 125 A rating holds flat from 40 °C to 50 °C. Above that it derates: 122 A at 55 °C, 120 A at 60 °C, 117 A at 65 °C, 114 A at 70 °C. The operating ambient range is -25 °C to +70 °C, storage from -40 °C to +80 °C. If the breaker sits in a hot switchroom or near a furnace line, use the 70 °C figure (114 A) for sizing — not the catalog 125 A. The TM240 release is calibrated for the thermal curve; the derating is already baked into the frame design, so you don't need to manually adjust the trip setting.