The Siemens 5SY4514-7CV is a 1+N miniature circuit breaker (MCB) in the 5SY4 series, rated 0.3 A with a C tripping characteristic and a 15 kA breaking capacity per IEC 60947-2. It switches the neutral conductor and fits a 2-module-width (36 mm) DIN-rail slot — common in European panel builds for lighting and small motor circuits where short-circuit protection up to 15 kA at 250 V AC is needed.
Ratings and what they mean for fit
The 0.3 A rated current (at 35 °C, per) means this MCB protects a very low-current branch — think control transformers, signal supplies, or small relay coils. Derate to 0.28 A at 40 °C and 0.24 A at 55 °C; if your panel ambient runs hot, the actual trip threshold shifts. The C-curve trips magnetically at 5–10× rated current, so it handles moderate inrush from contactors or small transformers without nuisance tripping. The 15 kA breaking capacity is the maximum fault current it can safely interrupt at 250 V AC — sized for most industrial sub-distribution boards where the prospective short-circuit current stays under that level. The 1+N design switches both line and neutral, with the neutral pole opening after the line pole — a requirement in some national wiring rules for final circuits. The 2-pole physical package takes up 36 mm (2 MW) on the DIN rail.
Deployment context
Snap-on mounting to a 35 mm DIN rail (: quick assembly system), any orientation. The 76 mm depth plus 70 mm installation depth means it sits flush with standard distribution board covers — no extra gland-plate clearance needed. IP20 with connected conductors is typical for enclosed panels; not rated for washdown or outdoor exposure.