The Siemens 3RH1122-2BC40 is a SIRIUS auxiliary contactor in size S00, designed for screw and snap-on mounting on a DIN rail or directly onto a contactor. It carries two instantaneous normally open contacts and two normally closed contacts, rated for AC-12 switching up to 10 A at 24 V, with a 30 V DC coil rated at 3.2 W holding power. The 45 mm width and 73 mm depth fit standard panel layouts, and the IP20 front enclosure keeps fingers out during commissioning.
Mounting and wiring
Mounts via the screw and snap-on method — you can clip it onto a 35 mm DIN rail or screw it directly to a panel backplate. The size S00 footprint is the smallest in the SIRIUS contactor family, so it leaves room for adjacent overload relays or bus bars. Wiring terminals accept solid conductors from 0.25 mm² up to 2.5 mm² (two conductors per clamp), which covers most control-circuit wiring without piggyback ferrules. Mounting position is flexible: ±180° rotation on a vertical surface, plus ±22.5° tilt forward or backward, so you can orient it to match the panel layout.
Environmental and electrical ratings
Operates from -25 °C to +60 °C ambient, and can be stored or transported from -55 °C to +80 °C. Shock resistance is 10g for 5 ms and 5g for 10 ms — enough for most industrial cabinets but not for direct mounting on a vibrating machine base. Pollution degree 3 means it handles conductive dust and condensation typical in control rooms and light industrial environments. The coil draws 3.2 W DC both during pick-up and hold, so no inrush spike to stress the control transformer. Surge voltage resistance is 6 kV, which gives solid margin for 400 VAC line transients.