What this 5SY4508-8 is and what it does
The Siemens 5SY4508-8 is a SENTRON miniature circuit breaker (MCB) — 2-pole, 1P+N configuration, rated 8 A at AC with a D tripping characteristic. The D curve means it tolerates high inrush currents (5–10× rated), so it's a fit for motor-starting or transformer loads where a B- or C-curve would nuisance-trip. Breaking capacity is 10 kA per EN 60898 and 20 kA per IEC 60947-2, giving headroom for industrial panel SCCR coordination. Overvoltage category III and pollution degree 3 suit it for fixed-installation distribution boards.
Thermal derating and ambient limits
The 8 A rating holds at 35 °C ambient. Above that, the thermal-magnetic trip derates linearly: 7.51 A at 40 °C, 7.26 A at 45 °C, 6.99 A at 50 °C, 6.72 A at 55 °C, and 6.43 A at 60 °C. If the panel runs hot (enclosed DIN rail, adjacent heat sources), size the load to the derated figure, not the nameplate. Operating range spans -40 °C to 75 °C, with humidity limits up to 95% at 55 °C.
Panel fit and mounting
Width is 36 mm (2 modular units), depth 76 mm, installation depth 70 mm. Mounts on DIN rail via the quick-assembly system in any position. Combined terminals top and bottom accept supply from either end. IP20 with connected conductors — suitable for enclosed distribution boards, not washdown zones. Halogen-free and silicon-free construction, sealable for tamper-proofing.
Lifecycle and sourcing
Current production — no end-of-life notice on record. The 5SY4508-8 is an active catalog line within the SENTRON family, so it's specified into new BOMs without a last-time-buy clock. Sourced to order against an RFQ through independent distribution; availability and current pricing confirmed at quote time.