The Siemens 5SJ6225-7FC is a SENTRON miniature circuit breaker (MCB) — 2-pole, C-curve, rated 25 A at 400 V AC, 50/60 Hz. Two poles give you simultaneous disconnection of both line conductors — needed for a 2-phase or split-phase circuit, or as a double-pole main on a single-phase subpanel. The 400 V AC rating covers standard 230/400 V three-phase networks; the 72 V DC maximum means it can also serve low-voltage DC loads like control circuits or small battery banks, though the DC breaking capacity is not separately listed.
Panel space and mounting
Width is 36 mm — that is 2 modular units (MW) on a standard DIN rail, so it occupies two 18 mm slots in a distribution board. Depth of 76 mm (70 mm installation depth) means it fits flush in most domestic enclosures without the cover hitting the breaker. Mount in any position; the -40 °C to +75 °C ambient range covers unheated plant rooms and outdoor cabinets in cold climates. Fine inside a clean panel; do not mount it exposed to washdown or outdoor spray without an IP-rated enclosure around it.