The Siemens SIRIUS 3RH1921-1FA22-ZW98 is an attachable auxiliary switch block designed to snap onto 3RT1 series power contactors and contactor relays. It adds four poles of auxiliary contacts — 2 normally open and 2 normally closed — to the base contactor, following the EN 50005 terminal numbering standard. Rated for a maximum current of 10 A, the auxiliary contacts carry a range of switching capacities across different voltage levels: 6 A at 24 V, 6 A at 125 V, 6 A at 230 V, 6 A at 250 V, 3 A at 400 V, and 0.3 A at 220 V. The contacts are rated for AC-15 duty at 690 V at 1 A, which covers solenoid and electromagnetic load switching typical in control circuits.
This part is a phased-out product. The manufacturer lists it as current but with a clear successor: the SIRIUS 3RH2 series. The 3RH1921-1FA22-ZW98 is sold in multi-unit packaging of 40 pieces. For new designs or BOM lines that need a long-term supply commitment, the 3RH2 series is the official replacement path.
The block snaps onto the front of a 3RT1 contactor and also onto the DIN rail via the contactor's own mounting foot. Dimensions are 44 mm wide, 51 mm deep, and 38 mm high — it adds minimal depth to the contactor assembly. Screw-type terminals accept 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²) with core-end processing, or 2x (20 to 16) and 2x (18 to 14) AWG.