What it is and where it fits
The Siemens 3RV2321-4EC10 is a SIRIUS circuit breaker designed specifically for starter combinations — meaning it integrates motor protection and disconnecting functions in one device sized for a motor branch circuit. It mounts via screw and snap-on onto 35 mm DIN rail per DIN EN 60715, so it lands in any standard control panel without special bracketry.
Key ratings and what they mean for your panel
Rated at 32 A continuous (at 480 V and 600 V), this breaker handles motor loads up to 20 hp at 460/480 V or 10 hp at 220/230 V. The breaking capacity tells the real story: 100 kA at 240 V AC, dropping to 25 kA at 400 V, 5 kA at 500 V, and 2 kA at 690 V. That 100 kA at 240 V means it can interrupt a high-fault utility feed on a 240 V panel without upstream fuses — but at 400 V you need to verify the available fault current stays under 25 kA, or add a current-limiting fuse ahead of it. Fuse backup is specified: gL/gG 63 A at 400 V, 500 V, and 690 V. That means if you need higher SCCR, a 63 A gL/gG fuse upstream lets this breaker ride through a fault up to the fuse's rating.
Integration and wiring
Mounting position is any, which simplifies panel layout. Clearance requirements: 50 mm above and below, 30 mm to the side, zero forward or backward. That 97 mm depth and 45 mm width mean it fits a standard 45 mm-wide DIN cell — one module wide. Main circuit terminals are screw-type, accepting 2x (1 to 2.5 mm²) or 2x (2.5 to 10 mm²) solid or stranded. M4 screws on the main contacts.