What it is and what it does
The Siemens 3RH1122-2BV40 is a SIRIUS auxiliary contactor in size S00, designed to switch control circuits and signal loads in industrial panels. The 36 V DC coil draws 3.2 W for both closing and holding, so the power supply budget is flat — no inrush spike to size around. Rated 10 A at 24 V for resistive loads, with a surge voltage withstand of 6 kV (pollution degree 3), it handles the dirty electrical environment you get in a mixed panel with drives and contactors.
Mounting and integration
Mounts via screw or snap-on onto DIN rail. The 45 mm width and 73 mm depth fit the standard S00 footprint — no surprises on the gland plate. Terminal accepts 2x (0.25... 2.5 mm²) solid or 2x (24... 14) AWG stranded. Mounting position allows ±180° rotation on a vertical surface and ±22.5° tilt forward/backward, so you can fit it into tight corners or angled subpanels without derating.
Contact configuration and switching reliability
Carries 2 instantaneous NO contacts and 2 NC contacts — no delayed, lagging, or make-before-break options on this variant. The contact reliability spec is one incorrect switching per 100 million operations at 17 V, 1 mA, which matters when you're switching PLC-level signals where dry contacts can oxidize. Mechanical life is 30 million operations typical.