What this Siemens 3VA2125-8HN46-0AA0 is and what it does
The Siemens SENTRON 3VA2125-8HN46-0AA0 is a 4-pole molded case circuit breaker (MCCB) rated for a continuous current of 25 A across the full ambient temperature range from 40 °C to 70 °C — no derating needed up to that ceiling. It's built for line protection duty, meaning it guards feeders and downstream distribution against short-circuit and overload faults. The interrupting capacity hits 440 kA at 240 V and still holds 330 kA at 415 V and 440 V, so it handles high-fault scenarios common in industrial switchboards and transformer secondaries. The ETU350 electronic trip unit gives you adjustable long-time pickup and delay (tr adjustable from 0.5 to 17 seconds), plus configurable N-conductor protection (OFF or 100%). That adjustability means you can coordinate selectivity with downstream breakers without swapping hardware — handy when you're freezing a BOM and need to dial in trip curves later.
Where it fits and how it mounts
At 140 mm wide, 181 mm tall, and 86 mm deep, this 4-pole MCCB fits standard distribution panel cutouts and leaves room for gland plates and cable bending radius. The IP40 front protection means it's fine in enclosed panels — not for washdown areas, but that's typical for switchgear. Mounting is via screw-on lugs or plug-in base; no DIN-rail snap-on here, so plan for a dedicated mounting plate.