The Siemens 3RH1131-1BF40 is a SIRIUS auxiliary contactor in size S00, carrying three normally-open instantaneous contacts and a 110 V DC coil that pulls 3.2 W closing and holding. It's a current-production part, so it's still a standard BOM line, not a scavenger hunt.
What the ratings mean for fit
The 45 mm width and 57.5 mm height fit the standard S00 footprint. Depth is 72 mm. Screw and snap-on mounting allows ±180° rotation on a vertical surface and ±22.5° tilt forward/backward. The three NO contacts are rated for switching at multiple voltages: 10 A at 24 V, 6 A at 230 V, 3 A at 400 V, 2 A at 500 V, and 1 A at 690 V. That covers most control and light power circuits in a panel. The contact reliability spec — one incorrect switching per 100 million operations at 17 V, 1 mA — means it handles dry logic signals without stuttering, so it's fine for PLC inputs or safety relay chains. Pollution degree 3 and surge voltage resistance of 6 kV mean it's rated for industrial environments where conductive dust or condensation is present. IP20 on the front keeps fingers out but doesn't seal against water — it's a panel-inside part, not a washdown component.