The Siemens 5SL6040-7 is a SENTRON miniature circuit breaker, rated 40 A with a C tripping characteristic, 1P+N poles, and a 6 kA breaking capacity certified to IEC/EN60898-1. It snaps onto a DIN rail, takes up one modular width (18 mm), and is designed for residential and infrastructure branch-circuit protection.
The 40 A rating at 30 °C is the headline number, but out here in the grease you need to watch the derating curve: at 40 °C ambient it drops to 38.08 A, and at 60 °C it's down to 33.9 A. For a residential or light commercial panel with typical fault levels under 6 kA, this holds up fine. It's a 1P+N design with neutral switching, meaning both line and neutral are broken when it trips — good for isolating the circuit during service. The unit is sealable and halogen-free, which matters if you're specifying for a panel that needs low-smoke, zero-halogen materials.
Physical fit and mounting
Width is 18 mm — one modular unit — so it takes up one slot on a standard DIN rail. Height 90 mm.