What this MCCB carries and what it protects
The Siemens SENTRON 3VA1225-4EF32-0AD0 is a 3-pole molded case circuit breaker (MCCB) rated 250 A continuous at 40 °C, with a TM240 thermal-magnetic overcurrent release. It is designed for line protection — meaning it sits at the feeder or main distribution point, not on a specific motor or load branch. The 121 kA breaking capacity at 240 V (75.6 kA at 415 V, 52.5 kA at 440 V) gives it the interrupting muscle to handle high-fault utility or transformer-fed panels without cascading failure upstream. Rated insulation voltage is 800 V, so it's comfortable in 480 V and 600 V class systems. The TM240 release is a fixed thermal-magnetic trip unit — no electronic adjustment, no communication module, no ground-fault monitoring. That keeps it simple and reliable for standard overcurrent protection, but means coordination studies rely on the fixed trip curve. Power loss at full load is 57 W max — factor that into enclosure ventilation if you're packing several breakers in a small panel.
Current derating and thermal reality
The 250 A rating holds flat from 40 °C through 50 °C. Above that, it derates: 243 A at 55 °C, 237 A at 60 °C, 230 A at 65 °C, and 223 A at 70 °C. If your panel ambient runs hot — say next to a drive cabinet or in a non-conditioned enclosure — the continuous current you can actually pull drops. The operating temperature range is -25 °C to 70 °C, with storage from -40 °C to 80 °C.
Mechanical fit and auxiliary options
Dimensions are 158 mm high, 105 mm wide, 70 mm deep. It mounts on a DIN rail or panel-mount base — standard SENTRON footprint. The basic switch supplied is order code 3VA12254EF320AA0, and it accepts up to 3 auxiliary switches (HQ type). No undervoltage release, no shunt trip, no voltage trigger — this is a bare-bones line protection breaker. If you need those accessories, you'll need to add them separately.