What this 0.3 A D-curve MCB is for
The Siemens 5SY6414-8 is a 4-pole miniature circuit breaker from the SENTRON 5SY6 series, rated at 0.3 A with a D tripping characteristic. That D curve means it tolerates high inrush currents — typically 10 to 20 times rated current for short periods — so it's sized for loads like small transformers, solenoid valves, or motor starters where the startup surge would nuisance-trip a B or C curve. The 0.3 A rating is a low-current branch; you'd see this protecting a control transformer secondary or a PLC power supply feed, not a main lighting circuit.
Breaking capacity: what the dual rating means
This breaker carries two breaking capacity ratings: 6 kA per EN 60898 and 30 kA per IEC 60947-2. The EN 60898 figure governs residential or light commercial distribution boards where the prospective fault current is lower. The IEC 60947-2 rating applies in industrial panels where the fault current at the bus can be higher. If you're specifying for a machine control panel, the 30 kA rating is the one that matters for SCCR compliance. At 400 V AC, that 30 kA gives you headroom in most industrial distribution without needing a current-limiting upstream device.
Panel fit and wiring
Mounts on DIN rail via the quick assembly system. The 4-pole body is 72 mm wide (4 width units). Terminal capacity accepts 0.75 to 35 mm² solid or stranded copper — that's a wide range, so it handles both fine control wiring and heavier power tails. Depth is 76 mm; installation depth 70 mm. IP20 with connected conductors, so it's standard for enclosed panel use. Mounting position is any, which helps in tight enclosures.
Environmental and compliance notes
Rated for ambient temperature -25 to +55 °C, storage -40 to +75 °C. Halogen-free and silicon-free construction. Sealable — useful for installations that need tamper evidence. Overvoltage category III, pollution degree typical for industrial panel environment. The part carries the standard Siemens SENTRON compliance documentation package (CE, RoHS, REACH).