What the interrupting ratings mean for panel coordination
The 3VA1125-4EF32-0AF0 is a Siemens SENTRON 3-pole molded case circuit breaker rated 25 A at 40 °C, with a TM240 thermal-magnetic release for line protection. Its interrupting capacity reaches 121 kA at 240 V, 75.6 kA at 415 V, and 52.5 kA at 440 V — numbers that tell you this breaker can clear high-fault currents in a low-voltage distribution board without upstream fuses needing to open first. That 121 kA at 240 VAC is the headline figure for North American panels where the available fault current is high; the 75.6 kA at 415 V and 52.5 kA at 440 V cover the European 400 V class. At 500 V and 690 V the rating drops to 11.9 kA, which still handles most motor-circuit faults but means you verify the point-of-supply SCCR if you're on a 690 V industrial grid.
Thermal derating — where the 25 A holds and where it drops
At 55 °C and 60 °C it derates to 24 A; at 65 °C and 70 °C it drops to 23 A. That flat 25 A band up to 50 °C is useful for panels with moderate internal temperature rise — you don't lose headroom until the enclosure runs hot.
Physical fit and internal switch configuration
The breaker measures 76.2 mm wide, 130 mm tall, and 70 mm deep — a standard SENTRON 3VA frame that fits the same panel cutout as other 3-pole 3VA units.