What it is and where it lands
The Siemens SIRIUS 3RH2911-1GA31-ZW97 is an auxiliary switch block that snaps onto the front of 3RH2 contactor relays — specifically the 3RH2140 and 3RH2440 frames. It gives you three normally-open and one normally-closed auxiliary contact set, wired through screw-type terminals, in a 36 mm wide package that clips onto standard DIN rail. Rated for 10 A maximum continuous current, with the AC-15 switching curve dropping to 6 A at 230 V and 3 A at 400 V. The DC switching side handles 10 A at 24 V, 6 A at 125 V, and 0.26 A at 600 V — so it covers both control-circuit and light power-switching duties inside the panel. Contact reliability is spec'd at one faulty switching per 100 million operations at 17 V, 1 mA — that's dry-circuit territory, meaning it'll handle PLC-level signals without the usual oxide-film issues. Mechanical life is 10 million switching cycles typical.
Panel fit and wiring constraints
Snaps onto the contactor relay front — no tools needed for the mechanical fit, but the screw terminals need a screwdriver. Accepts 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²) with ferrule, or 2x (20 to 16 AWG) and 2x (18 to 14 AWG) for stranded. Strip length isn't called out in the spec, but standard 8 mm works for this terminal class. IP20 on the front face — fine inside a closed panel, not for washdown or outdoor exposure. The operating temperature range is -25 to +60 °C, storage -55 to +80 °C. Insulation voltage is 690 V AC at pollution degree 3, with a 6 kV surge withstand rating.