The S202-B25 is a 2-pole miniature circuit breaker rated 25 A with Trip Curve B, meaning it trips between 3× and 5× rated current — designed for resistive and lighting loads where inrush is minimal, not motor starting. DIN rail mounting means it snaps into a standard 35 mm rail inside the distribution panel — no special adapter needed.
How it sits against the S202M-C25 sibling
The S202M-C25 shares the same 25 A, 2-pole, 277 VAC, 6 kA interrupting rating but uses Trip Curve C (5× to 10× In) instead of Curve B. That means the C-curve version tolerates higher inrush — better for small motor or transformer loads — while the B-curve S202-B25 trips faster on modest overloads, which is what you want for lighting panels or resistive heater circuits. Both mount on the same DIN rail footprint, so swapping one for the other in an existing panel is mechanically identical; the only change is the trip characteristic.