What it is and what the ratings mean
The Siemens SENTRON 5SY4140-6CC is a 1-pole miniature circuit breaker with B tripping characteristic, rated 40 A at 400 V AC. The B curve means it trips between 3 and 5 times rated current — suited for resistive or general lighting loads where inrush is modest. The 10 kA breaking capacity per EN 60898 tells you it can safely interrupt a fault current up to 10 kA without welding contacts or cascading upstream; that's standard for most sub-distribution boards in commercial and light industrial panels. For UL 1077 / CSA C22.2 No. 235 applications (supplemental protection), it's rated 5 kA — keep that in mind if the panel requires branch-circuit rated devices.
Mounting and wiring fit
Snaps onto DIN rail via the quick-assembly system — 18 mm width (1 module). Depth is 76 mm, installation depth 70 mm, so plan for a 90 mm deep enclosure minimum to leave wiring room. Terminals accept 0.75 to 35 mm² solid or stranded copper, with a listed tightening torque of 2.5 to 3.5 N·m. That 35 mm² top end is unusual for a 40 A breaker — it makes terminating larger supply feeders straightforward. Combined terminal at top and bottom; sealable cover is available for lockout/tagout.
Environmental and compliance
Rated IP20 with conductors connected — finger-safe but not sealed against moisture. Ambient operating range -25 to +55 °C; storage -40 to +75 °C. Halogen-free and silicon-free construction, which matters for clean-room or sensitive electronics environments. Overvoltage category III, energy limiting class 3. Touch protection is built in. The part is classified per DIN EN 61346-2 and DIN EN 81346-2 function code F.