What this MCB is and where it fits
The Siemens 5SY4120-6 is a 1-pole miniature circuit breaker from the SENTRON family, designed for branch-circuit protection in industrial control panels and building distribution boards. It carries a B tripping characteristic — instant trip between 3 and 5 times rated current — making it the standard choice for resistive and general-purpose loads where no high inrush from motors or transformers is expected. Rated breaking capacity is 10 kA per IEC/EN 60898-1 and 20 kA per IEC 60947-2, with a further 15 kA at DC (60 V per pole) per IEC 60947-2. That dual rating means it meets the higher fault-current demands of industrial panel coordination (60947-2) while also qualifying for residential and commercial final circuits under 60898-1. The 20 kA figure at 400 VAC gives real SCCR headroom for a 1-pole device — useful when the available fault current at the panelboard exceeds the typical 10 kA residential limit. Mounts on DIN rail via the quick-assembly system, occupies a single modular width (18 mm), and accepts any supply position. Depth is 76 mm (70 mm installation depth), so it sits flush with standard distribution board covers. The IP20 rating applies with conductors connected — expected for a panel-mount device.
Certifications and compliance
Certified to IEC/EN 60898-1 and IEC/EN 60947-2, with additional UL 1077 and CSA C22.2 No. 235 recognition (5 kA at AC). The part is halogen-free and silicon-free, rated for pollution degree 3 and overvoltage category III. The housing is sealable — a feature for panel builders who need to lock out adjustment after commissioning.
Environmental range
Operates from -40 °C to 75 °C ambient, with humidity derating: 95% RH up to 55 °C, 55% RH to 70 °C, and 35% RH to 75 °C. That -40 °C floor is relevant for unheated enclosures in cold climates or refrigerated areas.