The Siemens 3RH1122-2UB40 is a SIRIUS auxiliary contactor in size S00 — a compact 45 mm wide block that snaps onto DIN rail and wires up clean with screw terminals accepting 0.25 to 2.5 mm² solid or stranded. The 24 V DC coil pulls 3.2 W to close and holds at the same power, so no extra heat sink in a crowded panel. Rated for 10 A at 24 V (resistive), 6 A at 230 V, and 3 A at 400 V — these are the switching ratings that decide whether it handles your control or small motor circuit.
Ratings and what they mean for fit
The contact reliability spec — one incorrect switching per 100 million operations at 17 V, 1 mA — means this contactor can handle dry switching (low-voltage, low-current signals from PLC outputs or sensors) without needing a separate interface relay. Mechanical life is 30 million operations typical, so it outlasts most panel cycles. Pollution degree 3 (conductive pollution or dry non-conductive that becomes conductive) suits it for control panels in industrial environments without sealed enclosures. The IP20 front protection keeps fingers out but expects the panel to provide the rest of the ingress protection. Shock resistance is 10g for 5 ms and 5g for 10 ms — fine for machine-mounted contactors near presses or conveyors as long as they aren't directly on a hammering die. Operating temperature range -25 to +60 °C covers most plant-floor conditions short of a foundry wall.
Mounting and integration
Fastening method is screw and snap-on mounting — the 45 mm width clips onto standard DIN rail without tools. Mounting position allows +/-180° rotation on a vertical surface and +/-22.5° tilt forward/backward, so you can orient it for wire routing in tight enclosures. Depth is 73 mm, height 60 mm — leaves room in a 200 mm deep cabinet for wiring gutters.