What it is and what it does
The Siemens SENTRON 3VA1225-5EF42-0AB0 is a 4-pole molded case circuit breaker (MCCB) rated for 250 A at 40 °C, with a TM240 thermal-magnetic overcurrent release. It is designed for line protection in distribution panels. The 187 kA breaking capacity at 240 V means it can safely interrupt fault currents up to that level without upstream cascading — critical for high-fault installations near transformers or large motor banks.
Ratings that decide fit
Rated current holds flat at 250 A from 40 °C through 50 °C, then derates to 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 above 50 °C, the continuous load must be reduced accordingly. Breaking capacity varies with system voltage: 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. Match the interrupting rating to your available fault current at the point of installation. Insulation voltage is rated 800 V, and max power loss is 57 W — factor the heat into enclosure sizing.
Physical integration
Dimensions are 140 mm wide, 158 mm high, 70 mm deep. The 140 mm width on a 4-pole MCCB is standard for panelboard mounting; verify the busbar spacing and enclosure cutout against your existing layout. Comes with 2 auxiliary switches (HP design) factory-fitted. No undervoltage release, no ground-fault monitoring, no communication function — this is a straight line-protection breaker without add-ons.