SIRIUS coupling relay, S00 size — 24 VDC coil, 10 A rated
The Siemens 3RH2122-1QB40 is a SIRIUS coupling relay sized for auxiliary circuit switching, built on the S00 contactor footprint. It carries a 24 VDC coil with a varistor surge suppressor built in, and the main contacts are rated 10 A at 24 V — enough for pilot duty, signal isolation, or interposing between a PLC output and a larger contactor coil. The 45 mm wide body snaps onto standard 35 mm DIN rail or screws directly to a backplate, with ±180° rotation possible on vertical mounting surfaces and ±22.5° tilt forward/backward. Rated operational current drops with voltage: 4.7 A at 60 V, 3 A at 110 V, 1.2 A at 220 V, 10 A at 230 V, 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 — so the 10 A figure is specific to the 24 V and 230 V levels. The 2 NO + 2 NC instantaneous contact arrangement gives you two form C (changeover) sets for control logic or status feedback.
Panel integration — DIN rail, clearances, wiring
Mounts on 35 mm DIN rail via the integrated snap-on latch, or screw-fixed to a panel. The S00 body is 57.5 mm high, 45 mm wide, 73 mm deep. Clearance requirements: 10 mm upward, 10 mm forward, 10 mm downward, 6 mm at the sides — tight enough for dense control panels. Wiring terminals accept 2× (0.5 to 1.5 mm²), 2× (0.75 to 2.5 mm²), or 2× 4 mm² solid or stranded conductors. Pollution degree 3 rated, so it's suited for industrial environments where conductive dust or condensation may occur.