Siemens 3VA1225-6GF42-0JH0 — 250 A SENTRON MCCB for Line Protection
The Siemens 3VA1225-6GF42-0JH0 is a SENTRON molded case circuit breaker (MCCB) rated 250 A continuous, built for line protection in distribution panels. Four poles handle three-phase plus neutral, with an interrupting capacity of 220 kA at 240 V AC — that drops to 154 kA at 415 V, 75.6 kA at 440 V, 30 kA at 500 V, and 17 kA at 690 V, so the SCCR you can claim downstream depends on the system voltage you feed it. Rated insulation voltage is 800 V, which gives headroom for 690 V systems without derating the dielectric gap. The breaker carries a shunt trip (STL) release and comes with two auxiliary switches plus one trip alarm switch (HQ configuration) — enough for remote status and a separate alarm contact on fault.
Thermal Derating and Panel Fit
At 40 °C through 50 °C the breaker holds its full 250 A rating. 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 a sealed enclosure near a furnace line — that 223 A at 70 °C is the number to size against, not the nameplate 250 A. Footprint is 140 mm wide, 158 mm tall, 70 mm deep. That 140 mm width for a 4-pole 250 A frame is standard for SENTRON 3VA — it fits the same DIN-rail or mounting-plate cutout as other 3VA breakers in this frame class. The shunt trip adds a couple of terminals on the left side; plan for wire bending space around it.