What it is and what it does
The Siemens 5SL3325-7MB is a SENTRON miniature circuit breaker (MCB) with three poles, a C tripping characteristic, and a 25 A rated current at 400 V AC. It breaks fault currents up to 4.5 kA per EN 60898 — the standard that governs overcurrent protection in residential and commercial final circuits. The C-curve means it trips between 5 and 10 times rated current, so it handles moderate inrush from small motors or transformers without nuisance tripping, while still clearing a hard short fast enough to protect the downstream cable. Rated for use in residential buildings and infrastructure, it fits a standard 3-module-width DIN-rail slot (54 mm wide, 76 mm deep, 90 mm tall) and can be mounted in any orientation. The IP20 rating with connected conductors means it's protected against finger contact once wired, but it needs to live inside an enclosure — standard practice for this class.
What the ratings mean for fit
The 4.5 kA breaking capacity at 400 V AC is the figure that governs fault clearance in a residential or light-commercial panel. It's not a high-fault rating — if your service entrance has a prospective short-circuit current above 4.5 kA, you need a current-limiting upstream device or a higher-rated MCB. The C-curve is the standard choice for general-purpose socket circuits and small inductive loads; don't use it for purely resistive loads where a B-curve would give tighter protection, or for heavy motor starts where a D-curve is needed. Operating temperature range spans -40 °C to 75 °C, which covers unheated utility rooms and outdoor enclosures in most climates. The 2.2 W power loss per pole at rated current matters when you're packing multiple MCBs in a row — derating in a crowded enclosure is real, and that figure is what you use for the thermal budget. Sealable design lets you lock the toggle in the off position for lockout/tagout. Halogen-free and silicon-free construction means no corrosive off-gassing in a confined panel — relevant for installations near sensitive electronics or in process areas where silicone contamination fouls contacts.
Integration and mounting
Snaps onto standard 35 mm DIN rail. Three modular width units at 54 mm total width — plan your enclosure fill accordingly. Installation depth is 70 mm, so a 100 mm deep enclosure leaves enough finger-room for wiring. Supplementary devices (auxiliary switches, shunt trips, alarm contacts) can be ganged on the right side. Overvoltage category III and pollution degree 2 are the standard ratings for fixed-installation distribution boards — no special handling required beyond normal panel practice.