What it is and what it does
The Siemens SENTRON 5SY6114-7CC is a 1-pole miniature circuit breaker with a C tripping characteristic, rated 0.3 A at 35 °C. It breaks fault currents up to 6 kA per EN 60898 (5 kA per UL 1077/CSA C22.2 No. 235). The C-curve means it trips between 5 and 10 times rated current — a good fit for moderate inrush loads like small control transformers or relay coils where a B-curve would nuisance-trip but a D-curve would be too slow.
Where it fits in the panel
Occupies 1 modular width unit (18 mm) on a DIN rail. Depth is 76 mm, installation depth 70 mm. Mounting position is any, and the quick assembly system snaps onto the rail without tools. Combined terminals top and bottom accept wiring without separate ferrules for the neutral bar. Pollution degree 3 and overvoltage category III suit it for industrial control panels where conductive dust or condensation is possible.
Temperature derating — the real rating
The 0.3 A rating holds only at 35 °C. At 40 °C it derates to 0.28 A, at 45 °C to 0.26 A, at 50 °C to 0.25 A, and at 55 °C to 0.23 A. If your panel ambient runs above 35 °C, size the breaker for the derated value, not the label. The surrounding temperature influence also limits humidity: max 95% up to 55 °C, then 55% up to 70 °C, then 35% up to 75 °C.