The Siemens 3RH2122-1BG40-0AA6 is a SIRIUS auxiliary contactor in the S00 frame size, carrying two normally-open instantaneous contacts. It snaps onto a 35 mm DIN rail and can also be screw-mounted, so it drops into any standard control-panel layout without extra bracketry. Rated 10 A at both 24 V and 230 V, it handles the typical control-circuit loads — PLC outputs, relay coils, indicator lamps — across the common voltage levels in a panel. The 4 W DC coil draw (closing and holding) is low enough that a 24 VDC power supply can drive several of these without derating. Mechanical life is listed at 30 million operations, which for a contactor used in a cycling application (say, a conveyor interlock or a valve position feedback) translates to years of service before wear becomes a concern.
Mounting and clearances
The part occupies 45 mm width on the DIN rail, with a depth of 73 mm and height of 57.5 mm. Clearance requirements: 10 mm upward, 10 mm forward, 10 mm downward, and 6 mm to the side. That's tight enough to pack into a shallow enclosure, but the forward clearance means you need the gland plate or door to sit at least 10 mm clear of the contactor face. Mounting position is flexible — the contactor can be rotated ±180° on a vertical surface and tilted forward/backward by ±22.5°. That helps when the panel layout forces an odd orientation, though you still need to respect the clearance zones for arc quenching (arcing time 10–15 ms).
Environmental and compliance
Operating temperature range is -25 to +60 °C; storage goes from -55 to +80 °C. Pollution degree 3 means it's rated for industrial environments with conductive pollution or dry non-conductive pollution that becomes conductive due to condensation — standard for an uncoated control-panel contactor.
Wiring and termination
Terminals accept solid or stranded wire: 2× (0.5 to 1.5 mm²), 2× (0.75 to 2.5 mm²), or 2× 4 mm². That covers the common control-circuit wire sizes from signal-level up to power-feed for a small contactor coil.