The Siemens 3RA1220-1CD24-0BB4 is a SIRIUS non-fused reversing starter, size S0, designed to control the direction of a three-phase motor by switching two contactors in an interlocked arrangement. The unit ships as a pre-assembled kit that includes the contactor (3RT10 24-1BB40), the circuit breaker (3RV10 21-1CA10), the link module (3RA19 21-1BA00), and the RS assembly kit (3RA19 23-1D), so the integrator gets a coordinated set rather than piecing together components.
This reversing starter snaps directly onto 60 mm busbar systems (center-to-center spacing 60 mm), eliminating the need for separate DIN-rail mounting and reducing panel wiring time. The mounting position is horizontal, and the unit requires 30 mm clearance upward, 10 mm forward, 9 mm backward, and 30 mm at the side for airflow and cable routing — no clearance needed downward. Wire capacity on the main contacts accepts solid or stranded conductors from 1 to 6 mm², with dual-wire capability for 2x (1 to 2.5 mm²) or 2x (2.5 to 6 mm²), covering typical motor feed cables in this power class.
Environmental and operational limits
The unit operates reliably from -20 to +70 °C and can be stored or transported from -55 to +80 °C, which suits unheated warehouses or shipping in cold climates. Shock resistance is rated at 12.5g, and the pollution degree is 3, meaning it tolerates conductive pollution typical of industrial control panels without conformal coating.
No official successor has been issued for this order code, which is consistent with an active product that has not been superseded.