What the ratings mean for fit
The Siemens 5SY6314-8 is a SENTRON 5SY6 miniature circuit breaker, 3-pole, rated 0.3 A at 400 V AC with a D tripping characteristic. That D-curve means it tolerates the high inrush currents typical of motor and transformer loads — the magnetic trip threshold is 10–20× rated current, so it won't nuisance-trip on a starting compressor or a switched-mode supply bank. For a 0.3 A rating, that's a magnetic trip window of roughly 3–6 A instantaneous, which is appropriate for small inductive or capacitive loads where the inrush spike is brief but sharp. Breaking capacity is rated at 6 kA per EN 60898 and 30 kA per IEC 60947-2. The EN figure governs residential / light commercial distribution boards; the IEC figure applies when the breaker is used in industrial panels where the prospective fault current at the bus can be higher. For DC circuits, it carries 15 kA per IEC 60947-2 up to 72 V, and under UL 1077 / CSA C22.2 No. 235 it's rated 5 kA at AC — so it's recognized for North American supplementary protection applications as well.
Panel integration and mounting
Mounts via the quick-assembly system — snaps onto DIN rail, occupies 3 width units (54 mm). Installation depth is 70 mm; overall depth including terminals is 76 mm. Any mounting position is permitted, which simplifies layout in crowded enclosures. The breaker is sealable (provision for a lead seal or lockout tag) and carries touch protection on the terminals. Combined terminals (top and bottom) accept both busbar and conductor connections, and the supply cord position is unrestricted — wire from either end. Rated for 50/60 Hz, overvoltage category III. IP20 with connected conductors, so it's intended for enclosed panel use, not washdown or outdoor exposure.