What this MCCB is and what it does
The Siemens SENTRON 3VA1225-5EF42-0AG0 is a 4-pole molded case circuit breaker (MCCB) rated for line protection, carrying a rated continuous current Iu of 250 A. It uses a TM240 thermal-magnetic overcurrent release — the thermal element handles overloads, the magnetic element handles short-circuits. The interrupting ratings are 187 kA at 240 V AC and 121 kA at 415 V AC, so it can safely clear high-fault currents on industrial distribution without upstream cascading.
Current-carrying capacity across temperature
Full 250 A rating holds from 40 °C up to 50 °C ambient. Above that, the thermal trip curve derates: 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, size the load accordingly — the breaker won't nuisance-trip, but you lose headroom.
Physical fit and panel integration
Dimensions are 140 mm wide × 158 mm high × 70 mm deep. That 140 mm width is standard for a 4-pole MCCB in the 3VA frame — it needs a 4-module cutout on the DIN rail or mounting plate. Front face carries IP40 protection, so it's fine inside a closed panel but not for washdown or outdoor exposure.
Auxiliary contacts and release configuration
Comes with one auxiliary switch plus one trip alarm switch (HP type). No undervoltage release, no shunt trip, no ground-fault monitoring, and no communication module — this is a bare line-protection breaker. The auxiliary contacts are useful for remote status indication or interlocking; the trip alarm signals that the breaker has opened on a fault.