What it is and where it fits
The Siemens 3RH2122-2LJ80 is a SIRIUS coupling relay for switching auxiliary circuits, sized S00. It carries two N/O instantaneous contacts and a 24 VDC coil with an integrated varistor surge suppressor. Mounts via screw or snap-on onto 35 mm DIN rail — standard panel integration for control cabinets. Rated switching capacity is 10 A at 24 V, derating to 4.7 A at 60 V, 3 A at 110 V, and 1.2 A at 220 V. At 230 V it handles 10 A (likely resistive), then drops to 3 A at 400 V, 0.5 A at 440 V, 2 A at 500 V, 0.26 A at 600 V, and 1 A at 690 V. These are the contact ratings across the voltage range — match your load voltage to the right row.
Mounting and spacing
Fastening method is screw and snap-on onto 35 mm DIN rail. Mounting position allows +/-180° rotation on a vertical surface and +/-22.5° tilt forward/backward. Clearance requirements: 10 mm upward, 10 mm forward, 10 mm downward, 6 mm at the side. Dimensions are 73 mm deep, 45 mm wide, 70 mm high.
Environmental and compliance
Operating temperature range is -25 to +60 °C; storage range -55 to +80 °C. Pollution degree 3. Relative humidity minimum 10%. RoHS compliance date (substance prohibition) is October 1, 2009. The coil closing power at DC is 2.8 W.