The Siemens SIRIUS 3RH2122-2LB40-1LA0 is a size S00 auxiliary contactor with a 24 V DC coil, 2 NO instantaneous contacts, and an integrated varistor surge suppressor. It mounts via screw or snap-on onto 35 mm standard DIN rail in a standing position on a horizontal surface — a common panel layout for control cabinets. The 45 mm width and 70 mm height keep it compact for dense terminal blocks.
Contact ratings and what they mean for your circuit
The 2 NO contacts are rated across a wide voltage range. At 400 V AC the contact carries 10 A, at 230 V AC also 10 A, and at 690 V AC it carries 1 A. For DC switching, at 24 V rated value it handles 10 A, dropping to 0.26 A at 600 V. The 10 A at 400 V AC is the figure that governs most motor control circuit applications — it tells you the contact can reliably switch a typical 400 V control transformer or pilot load. The DC ratings are lower because DC arcs are harder to extinguish; the 7…20 ms arcing time reflects that. If you're switching a 24 V DC solenoid or contactor coil, the 10 A rating gives generous headroom.
Panel integration and clearances
The 116 mm depth fits standard enclosures with room for wiring behind the rail. Minimum clearances to adjacent components: 10 mm upwards, 10 mm forwards, 10 mm downwards, 6 mm at the side.