The Siemens SENTRON 5SY8240-8BB08 is a 2-pole miniature circuit breaker rated at 40 A with a D tripping characteristic, designed for 400 V AC systems. Its 25 kA breaking capacity per IEC 60947-2 handles high-fault industrial feeders, while the 5 kA rating per UL 1077 covers North American branch-circuit applications. The D-curve (10–20× In) suits motor and transformer inrush loads where a standard B or C curve would nuisance-trip.
Mounting and wiring
Snaps onto a DIN rail via the quick assembly system; the 36 mm width (2 width units) fits standard panel layouts. Accepts solid or stranded conductors from 0.75 to 35 mm² at the screw terminals, torqued to 2.5–3.5 N·m. IP20 with connected conductors means the busbars and terminations are touch-safe once wired — fine for enclosed industrial panels, not for wet washdown zones.