SENTRON 5SY7140-8 — 40 A D-curve MCB for high-inrush loads
The Siemens 5SY7140-8 is a 1-pole SENTRON miniature circuit breaker rated 40 A with a D tripping characteristic, designed for loads with high inrush currents — motor starters, transformers, or power-supply units where the start-up surge would nuisance-trip a B- or C-curve breaker. Per the datasheet, the D-curve magnetic trip threshold sits between 10× and 20× In, so it passes the initial spike and clears only on a sustained overload or hard short. Breaking capacity is 15 kA per EN 60898 and 20 kA per IEC 60947-2 at 400 V AC, with a separate 5 kA rating under UL 1077 / CSA C22.2 No. 235. That 20 kA IEC figure gives headroom for industrial panels where the prospective fault current at the distribution board runs above 10 kA — the 15 kA EN rating covers residential and light commercial installations. Rated voltage is 400 V AC (phase-to-phase or phase-to-neutral) and 72 V DC maximum. The single-pole form factor occupies one 18 mm width unit on a DIN rail, with quick-assembly mounting and any mounting position permitted. IP20 protection applies with connected conductors — standard for enclosed panelboard use, not for wet or washdown environments.
Lifecycle and sourcing posture
No official successor or replacement order code is listed. The part is part of the SENTRON 5SY7 series, which shares the same DIN-rail footprint and terminal layout as the 5SY4 series — a panel originally wired for a 5SY4140-7 can accept the 5SY7140-8 without rewiring, though the D-curve and breaking-capacity ratings differ between the two. Verify coordination with the upstream protective device if substituting.
Integration and compliance notes
Mounts on a DIN rail via the quick-assembly system — no tools needed for snap-on, but a screwdriver is required for the combined top and bottom terminals. Installation depth is 70 mm; overall depth is 76 mm. The 18 mm width (one width unit) fits standard distribution board spacing. Any mounting position is acceptable, and the housing is halogen-free and silicon-free — relevant for clean-room or sensitive electronic environments where outgassing must be controlled. Touch protection is built in (finger-safe terminals with conductors connected). The breaker is sealable for anti-tamper applications. Ambient temperature range is -40 °C to +75 °C, with humidity derating above 55 °C: max 95% RH at 55 °C, 55% at 70 °C, 35% at 75 °C. Overvoltage category III — suitable for fixed-installation distribution boards downstream of the service entrance. Compliance documentation covers RoHS and REACH (halogen-free and silicon-free construction). The UL 1077 / CSA C22.2 No. 235 listing at 5 kA covers North American supplementary protection applications. The EN 60898 and IEC 60947-2 ratings cover European and international installation standards.