What this MCCB is and what it does
The Siemens 3VA1225-6EF42-0AE0 is a SENTRON molded case circuit breaker (MCCB) rated for continuous current of 250 A across four poles. It's built for line protection — think main feeder or large subfeed in a distribution panel — not for motor or generator protection. The thermal-magnetic release (TM240) handles overload and short-circuit tripping without an external trip unit. Breaking capacity hits 220 kA at 240 V, 154 kA at 415 V, 36 kA at 440 V, and 17 kA at 690 V, so it's got headroom for high-fault industrial services where the available short-circuit current is stiff. The 4-pole construction means it switches all phases plus neutral — typical for TN-S or TN-C-S systems where you need full isolation. No undervoltage release, no shunt trip, no ground-fault module fitted from the factory; this is a straight thermal-magnetic breaker. The front face carries an IP40 rating, so it's fine inside a clean enclosure but not for washdown areas. Dimensions are 70 mm deep by 140 mm wide by 158 mm tall — standard 4-pole MCCB footprint for a 250 A frame.
Thermal derating and real-world current handling
Rated continuous current Iu is 250 A, but that's at 40 °C ambient. The 3VA1225-6EF42-0AE0 holds 250 A flat through 50 °C, then starts to taper: 243.3 A at 55 °C, 236.5 A at 60 °C, 229 A at 65 °C, and 223 A at 70 °C. If your panel ambient runs hot — say above 50 °C — you'll need to account for the drop. The storage range is -40 °C to 80 °C, and operating ambient goes from -25 °C to 70 °C. That's a wide window for most plant-floor conditions, but if the breaker lives in a non-ventilated enclosure near other heat sources, plan on the derated numbers.
What the auxiliary contacts give you
The breaker ships with four auxiliary switches (HQ type) already fitted. These are the early-make / late-break style used for status feedback to a PLC or for interlocking in a transfer scheme. No separate aux kit to order — it's on the breaker from the factory.