What it is and where it goes
The Siemens 3RH1122-1BP40 is a SIRIUS auxiliary contactor in size S00 — a 4-pole block with 2 N/O and 2 N/C contacts (instantaneous, no delayed or lagging poles). It mounts via screw or snap-on onto a DIN rail, and the mounting position allows ±180° rotation on a vertical surface plus ±22.5° tilt forward/backward, which gives panel builders flexibility in tight enclosures. At 45 mm wide and 72 mm deep, it fits the standard S00 footprint alongside its matching SIRIUS contactors.
What the ratings mean for your circuit
The headline rating is 10 A at AC-12 (resistive loads at 24 V), but the real-world switching capability varies by voltage and duty. At 230 V AC-15 (typical for solenoid valves and contactor coils) it's rated 6 A; at 400 V drops to 3 A, and at 690 V to 1 A. For DC switching, at 24 V it handles 10 A, at 110 V only 1 A, and at 220 V just 0.27 A — inductive DC loads need careful derating. The closing and holding power of the DC magnet coil is a flat 3.2 W, so the control transformer or 24 VDC supply must budget that per contactor.
Terminal and environmental limits
Screw terminals accept solid or ferruled stranded conductors: 2× 0.5–1.5 mm², 2× 0.75–2.5 mm², or 2× 4 mm². The front face is IP20 (finger-safe), so it's suitable for enclosed panels only — no washdown or outdoor exposure. Operating temperature range is -25 to +60 °C, storage and transport go from -55 to +80 °C. Shock resistance is 10g for 5 ms and 5g for 10 ms, which covers most industrial vibration profiles. Pollution degree 3 means it's rated for conductive pollution in industrial atmospheres.