Motor starting duty and the AC-3 rating that governs it
The 3RA2125-1GH24-0FB4 is a Siemens SIRIUS direct-on-line starter, Size S0, built around the 3RT2024-2FB40 contactor and the 3RA2921-2AA00 link module.
Panel fit and busbar mounting constraints
This starter snaps onto 60 mm busbar systems — the fastening method is integral, not a separate bracket. The mounting position is vertical only; the dimensions are 260 mm high by 45 mm wide by 165 mm deep. Clearance requirements: 50 mm upwards, 20 mm forwards, 10 mm downwards, and 20 mm at the side. Backwards clearance is zero — the unit sits flush against the mounting surface.
Thermal envelope and storage limits
During operation the ambient range is -20 to +60 °C, with temperature compensation active across that band. Storage and transport limits are wider at -50 to +80 °C. The 24 V DC coil (rated value 24... 24 V) draws its holding current through the link module; the supplied contactor is the 3RT2024-2FB40, which carries the same S0 frame size as the circuit-breaker section. The unit holds the line on a motor feeder provided the ambient stays within the operating envelope and the busbar system is rated for the bolted-fault current the upstream breaker can deliver.