SIRIUS 3RA2 direct starter — what it is
The 3RA2125-1FD24-0BB4 is a non-fused motor starter from the Siemens SIRIUS 3RA2 family, built as a direct starter with a thermal bimetallic overload relay (Class 10 trip). It comes pre-assembled with a 3RT2024-1BB40 contactor and a 3RA2921-1BA00 link module, so it wires up clean as a single unit on the rail.
Mounting and panel fit
Snaps onto 60 mm busbar systems (fastening method listed), mounts vertical only. The unit is 45 mm wide, 165 mm deep, 260 mm tall — that 45 mm width is one standard 9 mm module increment, so it takes up five modules on the DIN rail. Clearance needs: 30 mm upward, 10 mm forward, 10 mm downward, 9 mm at the side — backwards is zero, so it sits flush against the back panel. Wire range for main contacts is 1–10 mm² stranded, or 2x 2.5–6 mm².