What this SIRIUS direct starter delivers
The Siemens 3RA2120-1GD24-0BB4 is a SIRIUS direct online starter — a pre-assembled combination of a contactor and overload relay in one unit, size S0. The 24 VDC coil means it's ready for standard 24 V control systems without a separate transformer.
Mounting and panel fit — busbar snap-on
This starter is designed specifically for snapping onto 60 mm busbar systems — not DIN rail. The mounting position must be vertical. Dimensions are 165 mm deep, 45 mm wide, 260 mm high, so it fits into a standard S0 feeder slot. Clearance requirements: 50 mm upwards, 20 mm forwards, 0 mm backwards, 10 mm downwards, and 20 mm at the side — plan your enclosure depth and busbar layout accordingly. Main circuit connections use screw-type terminals — no cage clamps or spring terminals on the power side. The supplied contactor is a 3RT2024-1BB40, and the supplied link module is a 3RA2921-1BA00, so the overload relay and contactor arrive pre-wired as a matched pair.
Duty ratings and motor sizing across voltages
At 400 V AC-3, the starter handles 6.3 A — that's about 2.2 kW for a standard three-phase motor. At 480 V, it's also 6.3 A, which translates to 5 hp. At 600 V, same 6.3 A, good for 5 hp. On 230 V single-phase, it's rated 0.75 hp. The breaker size supplied is S00, which pairs with the S0 feeder size. Operating temperature range is -20 to +60 °C, with temperature compensation active across that band. Storage and transport range is -50 to +80 °C. No PROFIsafe or PROFINET IO protocol support on this variant — it's a standalone direct starter, not a fieldbus slice.