40 A C-Curve MCB for Branch Circuit Protection
The Siemens SENTRON 5SL4140-7CC is a 1-pole miniature circuit breaker rated 40 A at 400 V AC with a C tripping characteristic. Its 10 kA breaking capacity per EN 60898 means it can safely interrupt fault currents up to that level in residential and commercial branch circuits — adequate for most final sub-circuits where the prospective short-circuit current stays under 10 kA. The C-curve (tripping between 5× and 10× In) suits moderate inrush loads: lighting banks, small motorized equipment, and general socket outlets where the starting surge is higher than a B-curve would tolerate but lower than a D-curve allows.
Thermal Derating and Ambient Temperature
Full 40 A rating holds at 30 °C ambient. At 40 °C it derates to 36.96 A; at 50 °C to 33.64 A; at 55 °C to 31.85 A. If the panel runs hot — say adjacent to a transformer or in a non-ventilated enclosure — the actual continuous load must be reduced accordingly to avoid nuisance tripping.
Mechanical Fit and Panel Integration
Occupies 1 modular width unit (18 mm) on standard DIN rail. Depth is 76 mm, height 90 mm. Installation depth 70 mm. Mounting position any — no derating for horizontal or inverted orientation. IP20 with connected conductors, so it belongs inside a distribution board or enclosure, not exposed to washdown.