The Siemens 3RV2321-1HC20 is a SIRIUS circuit breaker designed specifically for starter combinations — it's the branch-circuit protection and disconnect in one package, sized for motor loads up to 8 A at 480 V or 600 V. The key number for panel coordination is the 100 kA short-circuit current rating at 400 V AC; that's the interrupting capacity you need to verify against the available fault current at the panelboard. It also carries 100 kA SCCR at 240 V, 42 kA at 500 V, and 6 kA at 690 V, so it holds up across common industrial voltages without needing an upstream current-limiting fuse.
Mounting and integration
Mounts via screw or snap-on onto 35 mm DIN rail per EN 60715, in any orientation — no derating for side or upright mounting. The 45 mm width (3 module spaces) and 97 mm depth fit standard distribution boards; clearance needs are 50 mm above and below, 30 mm to the side, zero forward or backward. Main circuit connections use spring-loaded terminals accepting 2x 1 to 10 mm² solid or stranded, terminated with a 3 mm screwdriver. That spring-cage saves panel build time vs screw clamps, but verify your ferrule length if using stranded.
What the ratings mean for fit
The 8 A rating at 480 V and 600 V sets the continuous current limit for the motor branch — pair it with a contactor sized for the same FLA. The 100 kA SCCR at 400 V means this breaker can safely interrupt a fault up to that level without upstream devices needing to clear first, which simplifies panel SCCR labeling per UL 508A. The switching rate is capped at 15 operations per hour under AC-3 duty (motor starting), adequate for most pump and fan cycles but not for frequent jogging. No ground-fault or phase-failure detection built in — those functions need an external relay or a different SIRIUS variant.
Temperature range
Rated for operation from -20 to +60 °C, storage and transport from -50 to +80 °C. The wide storage range matters for spares held in unheated warehouses or shipped in cold climates — the breaker can sit at -50 °C without damage, though it won't be rated to switch until it warms above -20 °C.