What it is and what it does
The Siemens 3RV2021-1DA25 is a SIRIUS motor protection circuit breaker designed for motor protection. It combines a circuit breaker and overload relay in one device, with phase failure detection built in — no separate overload block needed. Rated for CLASS 10 trip, it matches the thermal curve of standard induction motors and protects against overload, short-circuit, and phase loss. The 100 kA SCCR at 400 V (also at 240 V and 500 V) means it can safely interrupt fault currents up to that level without cascading upstream — a key spec for panel coordination studies. Mounts via screw and snap-on onto 35 mm DIN rail per DIN EN 60715, any position. The main circuit uses spring-loaded terminals (2x 0.5–2.5 mm² solid or stranded), so no screw torque check on the power side — just strip and push.
Integration fit
At 45 mm wide, 119 mm high, and 97 mm deep, it fits a standard 45 mm slot on a DIN rail — same footprint as the 3RV1011 series. Clearance: 50 mm above and below, 30 mm at the sides, 0 mm forward/backward — so it can butt against adjacent devices on the rail.
Ratings at a glance
Auxiliary contact ratings: 1 A at 24 V, 0.5 A at 120/125/230 V, 0.15 A at 60 V. Operating temperature -20 to +60 °C; storage/transport -50 to +80 °C. Maximum switching frequency 15 operations per hour at AC-3 / AC-3e duty. Motor horsepower ratings: 0.75 hp at 220/230 V, 0.5 hp at 200/208 V, 0.25 hp at 230 V, 0.1 hp at 110/120 V. Current settings: 3.2 A at 480 V and 600 V.