What it is and what it does
The Siemens 3RH1122-1AR00 is a SIRIUS auxiliary contactor — size S00 — designed to switch control signals and low-power loads in industrial panels. It provides two normally-open and two normally-closed instantaneous contacts, rated 10 A at 24 V and derated to 6 A at 230 V, 3 A at 400 V, and 1 A at 690 V. The contactor mounts via screw or snap-on onto a DIN rail, fitting a 45 mm wide slot.
Key ratings and what they mean for your panel
The 10 A rating at 24 V is the thermal current (Ith) — the continuous current the contacts can carry in free air. For motor control circuits, the switching capacity drops with voltage: at 230 V AC you get 6 A, at 400 V AC it's 3 A, and at 690 V AC it's 1 A. That means this contactor is suited for pilot-duty and control-circuit isolation, not direct motor switching. The 6 kV rated surge voltage resistance (impulse withstand) ensures it holds up against transient spikes on industrial lines without flashover. Mechanical endurance is rated at 30 million operations typical, and contact reliability is specified as one incorrect switching per 100 million operations at 17 V, 1 mA — a strong signal for PLC-level signal switching where low-energy circuits must not fail. The shock resistance of 10g / 5 ms and 5g / 10 ms covers most vibration environments on conveyors or machine tools.
Integration and mounting
The 45 mm width and 57.5 mm height fit the S00 footprint common across the SIRIUS family. Mounting position is flexible: +/-180° rotation on a vertical surface, plus +/-22.5° tilt forward/backward. The screw and snap-on fastening method lets you clip it onto a DIN rail without tools or bolt it down where vibration is higher. Wire sizes accepted range from 0.5 mm² up to 4 mm² solid, covering standard control wiring. IP20 on the front means it's protected against finger contact but not washdown — keep it inside a sealed enclosure.