What this MCCB brings to the panel
The Siemens 3VA1125-4EE46-0AA0 is a SENTRON molded case circuit breaker rated for 25 A continuous (Iu) with a 4-pole configuration and a TM220 thermal-magnetic release. The TM220 designation means the thermal element is fixed at the frame rating while the magnetic short-circuit pickup is adjustable — in this case up to 320 A (li max.), giving you room to coordinate with downstream branch protection without swapping the breaker body. Breaking capacity is the headline number here: 121 kA at 240 V AC, dropping to 75.6 kA at 415 V and 52.5 kA at 440 V. At 500 V and 690 V it still holds 11.9 kA. That 121 kA figure at 240 V means this breaker can sit upstream of a high-fault panelboard or a transformer secondary and still interrupt a bolted fault without welding its contacts — useful when the available fault current at the service entrance is in the 100 kA range. It's a line-protection version (Product version: Line protection) with no communication function and no ground-fault monitoring built in. If you need those, you're looking at a different variant in the 3VA family. The IP40 rating on the front means it's splash-resistant from the panel face but not washdown-rated — standard for indoor switchgear.
Duty and derating in the enclosure
Thermal derating is modest: the breaker carries 25 A at 45 °C and 50 °C, drops to 24 A at 55 °C and 60 °C, then to 23 A at 65 °C and 70 °C. That's a 2 A loss over a 25 °C rise — about 8% — so if your panel ambient runs hot near the upper operating limit of 70 °C, you still get 92% of rated current. The operating range is -25 °C to 70 °C; storage range is -40 °C to 80 °C. Physical footprint: 101.6 mm wide (4 in), 130 mm tall (5.12 in), 70 mm deep (2.76 in). That's a standard 4-pole MCCB width — it'll fit a SENTRON panelboard or a DIN-rail adapter without surprises. Power loss is 8.5 W maximum, which is low enough that you don't need forced ventilation in a typical enclosure, but group it with other high-loss devices and check the thermal budget.