What this MCB is and what it does
The Siemens 5SY4104-7CC is a SENTRON miniature circuit breaker (MCB) with a C tripping characteristic, designed to protect branch circuits against overcurrent and short circuits in industrial control panels and commercial distribution boards. The C-curve trips between 5 and 10 times rated current, making it a standard choice for moderate inrush loads like small motors, contactor coils, and lighting circuits where the startup surge is higher than a B-curve but lower than a D-curve. Rated breaking capacity is 10 kA at 230/400 VAC per EN 60898, which covers the majority of building-installation fault levels in Europe and many Asian markets. For UL 1077 / CSA C22.2 No.235 applications, the interrupting rating is 5 kA — a common derating when used as a supplementary protector in North American panels.
Physical fit and panel integration
Width is 18 mm — one modular unit on a standard DIN rail. Depth is 76 mm (70 mm installation depth behind the panel surface). Height is 90 mm. The quick-assembly fastening method and any mounting position mean it snaps onto the rail without tools and can be oriented vertically or horizontally inside the enclosure. IP20 with connected conductors — fine for dry indoor panels; not rated for washdown or outdoor exposure. Pollution degree 3 (conductive pollution or dry non-conductive pollution that becomes conductive due to condensation) and overvoltage category III (fixed installation downstream of the main distribution board) confirm it belongs in a closed, controlled environment.
Environmental and service life
Ambient temperature range from -40 °C to +75 °C covers cold storage and hot machine rooms. Humidity derating applies: max 95% RH at 55 °C, dropping to 35% at 75 °C — a typical curve for sealed electromechanical devices. Mechanical service life is 10,000 operating cycles, sufficient for most fixed-installation switchgear where the breaker is cycled infrequently. Halogen-free and silicon-free construction reduces toxic smoke and corrosive byproducts in a fire — relevant for panels in public buildings, data centers, or marine environments where these materials are restricted.