What this SIRIUS circuit breaker does in a panel
It's not a general-purpose branch breaker; it's sized and coordinated for the motor-starting duty cycle, with a rated operating frequency of 15 switching operations per hour at AC-3 (and AC-3e) maximum. Rated current lands at 12.5 A at both 480 V and 600 V, which maps to a motor output of 8 hp at 460/480 V and 10 hp at 575/600 V. The breaking capacity is the headline number here: 100 kA at 240 V and 400 V AC, dropping to 42 kA at 500 V AC and 6 kA at 690 V AC.
If you're comparing against the 3RV2411-1HA20, note the different breaking capacity curve and terminal configuration — the 3RV2411 is a different frame size. The 3RV2321-1KC20 is the 45 mm-wide SIRIUS frame for starter combinations; the 3RV2411 is wider and carries higher ratings. They are not drop-in interchangeable without rewiring and re-coordinating the panel.
Clearances and panel integration
Physical dimensions: 119 mm height, 45 mm width, 97 mm depth. Clearance requirements are specified for heat dissipation: 50 mm upward, 50 mm downward, 30 mm at the sides, and zero forward or backward clearance — meaning you can butt the device against the back panel and the enclosure door without additional air gap. That's useful for shallow enclosures. No ground fault or phase failure detection built in — this is a straightforward motor-protective circuit breaker, not a multifunction electronic relay. If you need those functions, they go in the overload relay or a separate monitoring module.