Siemens 5SY4120-7CC11 — 1P C-curve MCB at 20 A
The Siemens SENTRON 5SY4120-7CC11 is a 1-pole miniature circuit breaker with a C tripping characteristic rated at 20 A. It breaks fault currents up to 10 kA at 400 V AC per EN 60898, which covers the majority of commercial and industrial branch-circuit fault levels. The C-curve (5–10× In) is the standard choice for moderate inrush loads like small motors, transformers, and lighting banks — it holds through the start-up surge without nuisance tripping on resistive or lightly inductive circuits.
Panel fit and wiring
At 18 mm wide (1 width unit), this breaker snaps onto the DIN rail and occupies a single module slot in any SENTRON distribution board or enclosure. The terminals accept solid or stranded conductors from 0.75 mm² up to 35 mm², with a tightening torque range of 2.5 to 3.5 N·m — enough for the full range of branch-circuit wire sizes. Combined terminals top and bottom simplify daisy-chaining busbars or looping downstream loads. IP20 protection with connected conductors means it's suitable for enclosed panels; the sealable design lets you lock out unauthorized switching after commissioning.