What this part is and what it does
The Siemens SIRIUS 3RH1911-1HA01-ZW96 is an auxiliary switch block that snaps onto contactor relays and power contactors in the SIRIUS family. It gives you one normally-open and one normally-closed contact, rated to switch up to 10 A depending on the voltage — at 24 V it's good for 6 A, at 230 V also 6 A, and at 400 V it'll handle 3 A. The mechanical life is rated for 10 million switching cycles, and the contact reliability is one fault per 100 million operations at 17 V, 1 mA, so it's built for the long haul in a panel.
Mounting and wiring
This block snaps onto the contactor or relay — no tools needed for the mount, and it fits the standard DIN-rail footprint. The screw terminals accept 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²) with core-end processing, or the AWG equivalents 2x (20 to 16) and 2x (18 to 14). Front protection is IP20, so it's fine inside an enclosure but not for washdown areas. The block is 36.5 mm wide, 41.5 mm deep, and 37.5 mm high — it won't eat up much rail space.