What it is and what it does
The Siemens SIRIUS 3RH1122-1BF40-0AA6 is an auxiliary contactor — a control-circuit relay that extends the contact set of a main contactor or provides isolated signal feedback to a PLC. It carries 4 normally open and 2 normally closed instantaneous contacts, all rated for switching at 110 V DC coil voltage. The contacts are rated for 10 A at 24 V, 1 A at 110 V, 6 A at 230 V, 3 A at 400 V, 2 A at 500 V, and 1 A at 690 V — so the 110 V DC coil is the one to match, but the contacts can handle a wide range of AC and DC loads up to 690 V.
Where it fits and how it mounts
This auxiliary contactor is Size S00, meaning it occupies a 45 mm wide DIN-rail footprint — typical for control cabinets where space is tight. It mounts by screw or snap-on onto a standard 35 mm DIN rail, and the mounting position is flexible: it can be rotated ±180° on a vertical surface, and tilted forward or backward by ±22.5° on that same surface. That flexibility matters when you're squeezing it into a crowded panel next to a main contactor or a terminal block.
Wiring and environment
Terminals accept solid conductors: 2x 0.5…1.5 mm², 2x 0.75…2.5 mm², or 2x 4 mm², plus the AWG equivalents (2x 20…16, 2x 18…14, 1x 12). The front is rated IP20 — fine for a dry indoor panel, not for washdown. Operating temperature range is -25 to +60 °C, storage from -55 to +80 °C. Pollution degree 3 (conductive pollution or dry non-conductive that becomes conductive) means it's suited for industrial environments with moderate contamination. Shock resistance is 10g for 5 ms and 5g for 10 ms — enough for most machine-mounted applications but not for high-impact presses without additional isolation.