What it is and what it does
The Siemens 3RH1122-1BB40-ZW95 is a SIRIUS auxiliary contactor — a compact switching block used in control panels to extend the contact count of a main contactor or to switch pilot loads independently. Size S00 footprint (45 mm wide, 57.5 mm tall, 72 mm deep) fits standard DIN-rail enclosures, secured by screw or snap-on mounting. The 24 V DC coil draws a constant 3.2 W closing and holding power, so no coil economizer is needed for continuous duty. Rated operational current reaches 10 A at 24 V and derates to 1 A at 690 V — match the voltage to the load's insulation class.
Ratings and what they mean for fit
Two instantaneous NO contacts switch resistive or lightly inductive loads. Contact reliability is one incorrect switching per 100 million operations at 17 V, 1 mA.
Termination and wiring
Screw terminals accept solid conductors: two wires of 0.5…1.5 mm², two of 0.75…2.5 mm², or a single 4 mm² per clamp. AWG equivalents: 2x (20…16), 2x (18…14), 1x 12.