What it is and what it does
The Siemens 3RH1122-1AR10 is a SIRIUS auxiliary contactor in size S00, built to switch control signals and low-power loads in a panel. It carries 2 normally open instantaneous contacts rated for 10 A at 24 V in AC-12 duty — that's the resistive load curve for pilot lights, contactor coils, and PLC inputs. The AC-12 rating is the one that governs real-world fit for control circuits; the 10 A figure at 24 V tells you it can handle a bank of contactor coils without an interposing relay. Rated operational current drops with voltage as you'd expect: 6 A at 230 V, 3 A at 400 V, 2 A at 500 V, 1 A at 690 V. That's the same contact stack, just derated by the switching arc energy. For 110 V control circuits it's rated 1 A. These numbers come from the maker's own table — match the voltage on your BOM line to the right row before you commit the part.
Mounting and wiring
Fastens with a screw or snaps onto a DIN rail — pick whichever the panel layout prefers. The 45 mm width and 57.5 mm height fit the standard S00 footprint; depth is 72 mm including clearance for the terminals. Mounting position is flexible: +/-180° rotation on a vertical surface, and you can tilt it forward or backward by +/-22.5° if the gland plate forces an angle. Terminal accepts solid conductors: 2x 0.5–1.5 mm², 2x 0.75–2.5 mm², or 2x 4 mm². AWG equivalents are 2x 20–16, 2x 18–14, or 1x 12. That's enough cross-section for daisy-chaining through multiple aux contacts without a separate terminal block. IP20 on the front means it's protected against finger contact — standard for a closed panel, but keep it behind a door if the enclosure sees washdown.
Lifecycle and sourcing
RoHS compliance date is marked as July 1, 2006, which aligns with the EU RoHS directive. Surge voltage resistance is rated at 6 kV, and the pollution degree is 3 (conductive pollution or dry non-conductive that becomes conductive). That's typical for industrial control panels but worth noting if the environment is unusually dusty or humid.