What this breaker is and what the ratings mean for your panel
The S201-K25 is a 1-pole miniature circuit breaker from ABB's S200 series, rated 25 A at 277 V AC. The Trip Curve K means the magnetic trip operates between 10 and 14 times the rated current — designed for loads with moderate inrush, like motor starters or transformer primaries, where a Curve C might nuisance-trip on startup but a Curve D would be too slow for branch protection. The 6 kA interrupting rating at 277 V AC is the maximum fault current it can safely clear; for a 480Y/277 V panel, this breaker sits on the 277 V line-to-neutral leg, so the available fault current at that point must be 6 kA or less — check your SCCR study before committing the BOM line.
Mounting and approvals — what the nameplate tells you
Snaps onto standard DIN rail. The UL 1077 listing classifies it as a supplementary protector — it's not a service-entrance breaker; it protects downstream equipment inside a listed industrial control panel. CSA 22.2 covers Canadian installations. The S200 series shares a common footprint, so if you're swapping an older S200 unit, the bus-bar pitch and terminal spacing are the same. Terminal torque: 2 Nm for the line and load lugs, accepts up to 25 mm² copper.