SENTRON 5SP3425-3 — 4-pole E-curve MCB, 25 A, 25 kA
The Siemens 5SP3425-3 is a SENTRON main miniature circuit breaker, 4-pole, rated 25 A with an E tripping characteristic and a 25 kA breaking capacity at 400 V AC per EN 60898. That 25 kA interrupting rating means it can clear a bolted fault on a 400 V distribution board without the upstream fuse needing to open — selectivity headroom for a sub-main. Six modular width units (MW) wide, 128 mm tall, 76.3 mm deep into the enclosure.
Thermal derating and ambient limits
Rated 25 A at 30 °C ambient. At 40 °C it's 23.75 A; at 45 °C, 23.125 A; at 50 °C, 22.5 A; at 55 °C, 21.875 A. That's a 12.5 % drop from 30 °C to 55 °C — plan your panel thermal budget accordingly if this breaker sits near transformers or drives. Operating range is -40 °C to 70 °C, so it handles outdoor enclosures in cold climates without issue.
Mounting and wiring
Snaps onto standard DIN rail (35 mm). Terminals accept 2.5 mm² to 50 mm² solid or stranded copper — that's big enough for a 25 A feed on a sub-distribution board. Saddle terminals and box-terminal infeed are both present; the integrated locking slide accepts a padlock, wire seal, or cable tie for lockout/tagout. Pollution degree 3, overvoltage category IV — rated for the harsh side of the main distribution panel.