What it is and where it fits
The Siemens 3VA1225-5EF32-0DA0 is a SENTRON molded case circuit breaker (MCCB) for line protection, carrying a TM240 thermal-magnetic release and a 250 A rating at 40 °C. It is a 3-pole unit with an undervoltage release (UVR) built in, sized for main feeder or large subfeed protection in industrial distribution panels.
Breaking capacity — what the numbers mean
This MCCB delivers 187 kA at 240 V, 121 kA at 415 V, 75.6 kA at 440 V, 30 kA at 500 V, and 17 kA at 690 V. These are the interrupting ratings at each voltage level — the breaker can safely clear a fault up to that current without welding contacts or rupturing the case. For a 480 V panel, the 75.6 kA figure is the one that governs SCCR coordination with upstream gear.
Thermal derating — continuous current vs. ambient
Rated 250 A from 40 °C through 50 °C ambient. Above that, the TM240 release derates: 243 A at 55 °C, 237 A at 60 °C, 230 A at 65 °C, 223 A at 70 °C. If the panel ambient runs hot, size the breaker for the actual enclosure temperature — not the nameplate 250 A. The rated insulation voltage is 800 V, with operation from -25 °C to 70 °C.
Physical fit and panel integration
Dimensions are 105 mm wide, 158 mm high, 70 mm deep. It mounts on a DIN rail or directly to a backplate in a standard MCCB footprint. The 3-pole form factor with integrated undervoltage release means one less auxiliary to wire separately — the UVR coil is factory-installed, so verify control voltage matches the panel's trip-coil supply.
Power loss and thermal budget
Maximum power loss is 59.5 W at rated current. That heat stays inside the enclosure — factor it into the panel's thermal calculation, especially if the MCCB is grouped with other high-current devices in a sealed cabinet.