The Siemens SIRIUS 3RV2021-4DA15 is a motor-protective circuit breaker designed for Class 10 trip response. It's the part that sits between your contactor and the motor, sized to protect a 3 hp load at 230 V. Any mounting position works, which simplifies panel layout when you're packing breakers into a tight gland plate. That's a critical feature for a motor-protective breaker on a three-phase line: if one phase drops, the breaker trips before the motor single-phases and cooks the winding. No ground fault detection on this variant, so if that's required you'd look at a different order code in the 3RV2 family.
The interrupting rating varies with system voltage: 100 kA at 240 V, 25 kA at 400 V, 5 kA at 500 V, and 2 kA at 690 V. On a 480 V system the continuous current rating is 25 A. That 25 kA at 400 V is the figure most panel builders will check first — it tells you whether this breaker coordinates with the downstream contactor and upstream feeder in a 400 V distribution.
Duty cycle and temperature range
Rated for 15 switching operations per hour at AC-3 (motor) duty. That wide storage range matters if the spare sits in an unheated warehouse through a winter shutdown — the breaker won't degrade from cold soak. The operating range covers most mill environments, but if your panel is in a steam trench or directly above a dryer section, check that the internal temperature stays under 60 °C.
Main contact terminals accept M4 screws. Wire range 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²) solid or stranded. That covers standard motor leads up to 2.5 mm² — if your motor is pulling more than 25 A continuous, the wire gauge would be larger and you'd step up to the next frame size. Auxiliary contact ratings: 1 A at 24 V, 0.5 A at 120/125/230 V, 0.15 A at 60 V.
Lifecycle status is current — this is an active catalog item in the SIRIUS line. No last-time-buy or phase-out notice is in effect for this order code.