What this MCCB carries — and what it means for your panel
The Siemens SENTRON 3VA1125-5EF32-0HC0 is a 3-pole molded case circuit breaker rated for 25 A continuous current at 40 °C, with a TM240 thermal-magnetic overcurrent release and an integrated shunt trip (STL) for remote tripping. Its breaking capacity hits 187 kA at 240 V AC, 121 kA at 415 V, and 75.6 kA at 440 V — numbers that tell you this breaker handles high-fault utility feeds or transformer secondaries without cascading upstream. The 800 V rated insulation voltage (Ui) means it's comfortable in 480 V and 600 V class panels, and the 2 HQ auxiliary switches give you status feedback for a PLC or annunciator without adding a separate contact block.
Breaking capacity by voltage — selectivity planning
The 187 kA at 240 V is the headline number, but the real-world selectivity decision lives at 415 V (121 kA) and 440 V (75.6 kA). At 690 V it drops to 17 kA — still enough for most 690 V motor branch circuits, but you'll want to verify the available fault current at the panelboard. The TM240 release is fixed thermal-magnetic, not electronic, so coordination curves are straightforward: thermal pickup starts around 1.05× In, magnetic instantaneous typically 10× In. Pair it with a downstream 10–16 A MCB for full selectivity up to about 10 kA.
Panel fit and mounting
The 3VA frame mounts on a DIN rail or direct panel via screw terminals. Dimensions: 130 mm height, 76.2 mm width (about 3 inches — three 1-inch pole spaces), 70 mm depth. The IP40 front protection means it's fine in a standard enclosure with a door; no washdown rating, so keep it out of wet areas. The 2 HQ auxiliary switches are wired to terminals on the breaker face — no extra enclosure space needed.
Thermal derating — don't crowd it
The 25 A rating holds flat from 40 °C to 50 °C. At 55 °C it derates to 24 A, at 60 °C to 23.5 A, at 65 °C to 23 A, and at 70 °C to 22.5 A. If the breaker sits next to other heat sources in a crowded panel, use the 55 °C column for your continuous load calculation — that's where the curve starts to bite. Operating range is -25 °C to 70 °C; storage from -40 °C to 80 °C.