What it is – and what the ratings mean for fit
The Siemens 3RV2021-4CA10 is a SIRIUS-branded motor-protective circuit breaker designed for branch-circuit protection of three-phase motors. Its trip class 10 ensures fast overload clearing during start-up without nuisance trips on normal acceleration curves. The 45 mm width and 97 mm depth fit standard DIN-rail grids – two units per 22 mm slot pitch. Screw and snap-on mounting per DIN EN 60715, any position allowed. Ambient range -20 to +60 °C operating; storage down to -50 °C. Terminals are M4 screw-type for the main current circuit, accepting 2x (1…2.5 mm²) or 2x (2.5…10 mm²) solid or stranded.