What it is and what it does
The Siemens 5SJ4115-8HG41 is a 1-pole SENTRON miniature circuit breaker with a D tripping characteristic, rated 10 kA breaking capacity per EN 60898 and 15 kA per IEC 60947-2. That D-curve means it's built for loads with high inrush — motor starters, transformers, solenoid banks — where the magnetic trip kicks in at 10–20× rated current, so nuisance tripping on startup is less likely than with a B or C curve.
Fit and footprint
It snaps onto standard DIN rail (35 mm profile) in any mounting position, takes up one modular width unit (18 mm wide), and extends 70 mm deep into the enclosure — a shallow enough footprint for tight gland-plate clearance. The combined terminal top and bottom accept Cu conductors with a tightening torque of 3.5 Nm, no tunnel terminals to mess with.
Where it lives
Rated for pollution degree 3 and overvoltage category III, so it's comfortable in industrial control panels — not just clean dry indoor switchgear. Ambient range from -40 °C to 75 °C, with up to 95% humidity; the IP20 rating applies with conductors connected, IP40 in the handle area. Halogen-free and silicon-free construction matters for environments sensitive to outgassing (clean rooms, food processing).