The Siemens 5SL3125-7MB is a SENTRON miniature circuit breaker, single-pole, with a C tripping characteristic rated at 25 A. It breaks fault currents up to 4.5 kA per EN 60898 at 230/400 V AC, which covers the standard residential and light commercial service-entrance fault levels. The C curve means it holds through moderate inrush — think motor-start or capacitor-bank loads — without nuisance tripping, while still clearing fast on a hard short.
Footprint and panel fit
Occupies one 18 mm modular width unit on a DIN rail. Depth is 76 mm, installation depth 70 mm, so it sits flush in any standard distribution board. Mounting position is unrestricted — vertical, horizontal, upside-down in a tight enclosure — the thermal-magnetic trip doesn't care. IP20 with conductors connected, which is the norm for a panelboard interior; no washdown rating here.
What the ratings mean for the buyer
The 4.5 kA breaking capacity per EN 60898 is the standard for most residential and light commercial final circuits in Europe — it's sized for the typical prospective short-circuit current at the board. If your installation requires a higher SCCR (say 6 kA or 10 kA), you'd step up to the 5SL6 or 5SL4 series. The 25 A rating is common for cooker circuits, shower feeds, or sub-distribution. Power loss is 2.2 W per pole at rated current in hot state — negligible for thermal budgeting in a populated board.