What this part is and where it fits
The Siemens 3RH1122-1AP00 is a SIRIUS auxiliary contactor in size S00, used to switch control and auxiliary circuits inside motor control centers and panel stacks. Its 45 mm width and 72 mm depth let it slot into existing S00 footprints without re-drilling the backplate. Mounting is screw or snap-on, so a failed unit can be swapped inside a live panel safely. Two instantaneous normally open contacts are rated for high reliability at low signal levels: one incorrect switching per 100 million operations at 17 V and 1 mA. That makes this contactor well-suited for PLC input circuits or other dry-switching applications where oxide films can cause intermittent failures. Front-face protection is IP20, which meets the usual requirement for enclosed panel mounting. The device is rated for pollution degree 3, meaning it handles conductive dust and condensation in typical industrial environments.