Integrator note — 5SL4240-7CC
The Siemens SENTRON 5SL4240-7CC is a 2-pole miniature circuit breaker with a C tripping characteristic, rated 40 A at 400 V AC and 10 kA breaking capacity per EN 60898. That 10 kA figure is the short-circuit capacity the breaker can safely interrupt at its rated voltage — critical for verifying SCCR on the panel label. The C-curve means magnetic trip occurs at 5 to 10 times rated current, so it's sized for moderate inrush loads like small motors, lighting banks, and transformer primaries where you need some tolerance for starting current without nuisance trips. The 2-pole design (2 MW units wide, 36 mm) gives you a switched neutral or a 2-phase feed in a single module.
Thermal derating and real-world current
Rated 40 A at 30 °C ambient. At 40 °C it's 36.96 A, at 45 °C it's 35.34 A, at 50 °C it's 33.64 A, and at 55 °C it's 31.85 A. If the panel ambient runs hot — say near a drive cabinet or a transformer bay — use the 50 °C figure for your load calculation. The breaker's thermal-magnetic element is calibrated to these derated values; ignoring them means nuisance tripping on a warm day.
Mounting and environment
Snaps onto standard 35 mm DIN rail. Depth is 76 mm overall, installation depth 70 mm. Mounting position is any, so horizontal DIN-rail layouts in shallow enclosures are fine. Pollution degree 2 (normal industrial environment, no condensation). Overvoltage category III — suitable for fixed installation downstream of the main distribution board. Vibration rated 50 m/s² from 25 to 150 Hz per IEC 60068-2-6, so it holds up on machine-mounted subpanels. IP20 with connected conductors — keep it inside a closed cabinet.
Lifecycle and compliance
Listed as current production — no end-of-life notice on this variant. The 5SL4 series is Siemens' standard residential and light-commercial MCB line. Halogen-free and silicon-free construction, which matters for clean-room or semiconductor-adjacent installs where outgassing contaminates optics or wafers. Sealable (can be padlocked in OFF position for lockout/tagout). Suitability for residential buildings and infrastructure per the manufacturer's classification.