The ABB S804S-C20 is a 4-pole miniature circuit breaker from the S800S series, rated 20 A with a Trip Curve C characteristic. The 20 A rating means it carries continuous resistive and motor loads up to that current without nuisance tripping, while the C-curve (5–10× In magnetic trip) handles moderate inrush from small motors, transformers, and lighting banks — typical for mixed industrial loads in a sub-distribution board. The 50 kA interrupting capacity at 230 VAC is the key figure for a plant engineer: it tells you this MCB can safely clear a fault up to 50 kA without welding its contacts or cascading upstream, which is essential for high-fault installations near large transformers or in industrial switchgear.
Snaps onto standard DIN rail in the enclosure — 4-pole width means it occupies four modular spaces (72 mm at 18 mm per pole). For a panel-builder wiring a sub-distribution board, the S800S footprint is consistent across the series, so busbar and comb-bridge layouts stay predictable. Rated 230 VAC line-to-line or line-to-neutral; the 50 kA SCCR holds across that voltage, so no additional current-limiting fuse is needed upstream in most configurations.