The Siemens 3RV2321-1JC10 is a SIRIUS circuit breaker designed specifically for starter combinations — meaning it integrates directly into a motor starter assembly, combining short-circuit and overload protection in one device. It is rated for a voltage range of 20 to 690 V and delivers a breaking capacity of 100 kA at 400 V AC, which covers most industrial distribution faults without needing an upstream fuse. Mounting is via screw or snap-on onto a standard 35 mm DIN rail per DIN EN 60715, and the 45 mm width means it occupies a single 45 mm module slot in a panel — a compact footprint for a 100 kA-rated device. The operating temperature range is -20 to +60 °C, with storage from -50 to +80 °C, so it handles unheated warehouses and panel environments.
Breaking capacity across voltages
The 100 kA rating at 240 V and 400 V AC is the headline figure — it means this breaker can safely interrupt a fault current up to 100,000 A at those voltages, which is typical for high-capacity industrial mains. At 500 V AC the capacity drops to 42 kA, and at 690 V AC it is 4 kA — still adequate for most motor branch circuits at that voltage, but worth noting if your system fault current exceeds 4 kA at 690 V.
Panel integration and wiring
The 45 mm width and 97 mm depth fit a standard 45 mm DIN-rail slot. Wiring is via screw-type terminals on the main current circuit, accepting 2x (1 to 2.5 mm²) solid/stranded or 2x (2.5 to 10 mm²) — so you can land both supply and load conductors on the same terminal. The mounting position is any, which simplifies panel layout.