What it is and where it fits
The Siemens 3RV2321-1HC10 is a SIRIUS-branded circuit breaker designed specifically for starter combinations — meaning it integrates directly into motor starter assemblies, combining short-circuit and overload protection in one device. It mounts via screw or snap-on onto 35 mm DIN rail per DIN EN 60715, with a 45 mm width and 97 mm cube footprint, so it fits standard panel layouts without extra adaptors.
Interrupting capacity — what the numbers mean
Rated interrupting capacity hits 100 kA at 240 V and 400 V AC, 42 kA at 500 V, and 4 kA at 690 V. The 100 kA figure at 400 V means this breaker can safely clear a fault up to 100,000 symmetrical amps without welding contacts or cascading damage upstream — critical for high-fault panels near large transformers. At 690 V the rating drops to 4 kA, so verify the available fault current at that voltage before specifying.
Panel integration and wiring
Screw-type terminals on the main current circuit accept 2x (1–2.5 mm²) solid or stranded, or 2x (2.5–10 mm²). Main contact screws are M4. Any mounting position allowed. Clearance: 50 mm above and below, 30 mm at the sides, zero forward or backward — so it nests tight against adjacent devices.