The Siemens SENTRON 5SP3325-3 is a 3-pole miniature circuit breaker (MCB) with an E tripping characteristic, rated at 25 A and 25 kA breaking capacity at 400 V AC. It is designed as a main miniature circuit breaker for residential buildings and infrastructure applications, per the manufacturer's classification. The E characteristic means it is designed for cable and line protection in installations where inrush currents are moderate — a middle ground between the more common B and C curves, offering a wider magnetic trip threshold that reduces nuisance tripping on transformer or capacitive loads while still protecting against short circuits.
At elevated ambient temperatures the breaker derates: 23.75 A at 40 °C, 23.125 A at 45 °C, 22.5 A at 50 °C, and 21.875 A at 55 °C. If your panel runs hot, size the load accordingly — the 25 A nameplate applies only up to 30 °C. The 25 kA breaking capacity at 400 V AC (per EN 60898) means this breaker can safely interrupt a fault current up to 25,000 A without welding its contacts or failing catastrophically. That is a high-interrupting rating for a residential/infrastructure MCB — suitable for installations with high prospective short-circuit current, such as near a transformer substation. This is not a downstream sub-panel device; it belongs at the origin of the installation.
The breaker occupies 4.5 modular width units (MWUs) — at 18 mm per MWU, that is 81 mm of rail space. Plan your enclosure layout accordingly; this is wider than a standard 1-pole MCB (which takes 1 MWU) because it is a 3-pole unit with a higher interrupting capacity. Dimensions: 128 mm height, 76.3 mm depth (including enclosure depth). Saddle terminals are standard; the infeed can be at the box terminal. The breaker is sealable and lockable via an integrated locking slide, accepting a lock, wire seal, or cable ties — useful for utility metering or tamper-proof installations.
For BOM freeze or multi-year project planning, this part carries no imminent obsolescence risk.