What it is and where it fits
The Siemens 3RH2140-1BW40-0AA6 is a SIRIUS auxiliary contactor in size S00 — a compact 45 mm wide block that adds 4 normally-open instantaneous contacts to a motor starter or contactor assembly. It snaps onto 35 mm DIN rail or screws directly to a mounting plate, and the coil pulls 4 W closing and holding at 48 V DC. Rated 10 A at 24 V and 10 A at 230 V, it handles signal-level switching across control circuits up to 690 V. The 73 mm depth leaves room for wiring in shallow enclosures.
What the ratings mean for the panel
The 4 NO contacts are rated for AC switching at 10 000 operations per hour with an arcing time of 10 to 15 ms, and DC arcing runs 7 to 13 ms — fast enough for relay logic and PLC input isolation. Mechanical life is 30 million operations typical, so it outlasts most control transformers in the cabinet. Pollution degree 3 means it tolerates conductive dust in industrial panels without conformal coating. Mounting position is flexible: ±180° rotation on a vertical surface, and ±22.5° tilt forward or backward. Clearance requirements are 10 mm upward, downward, and forward, and 6 mm to the side — tight enough for dense DIN-rail layouts. Wire sizes from 0.5 to 4 mm² solid or stranded fit the screw terminals, with dual-wire entry up to 2.5 mm².