SIRIUS S00 coupling relay — what it is and where it lives
The Siemens 3RH2122-2VB40 is a SIRIUS coupling relay in the S00 contactor frame size — essentially an auxiliary contactor block with a 24 VDC coil and a built-in diode surge suppressor across the coil terminals. It mounts via screw or snap-on onto a 35 mm DIN rail, and the mounting position allows ±180° rotation on a vertical surface plus ±22.5° tilt forward/backward — useful when you're squeezing it into a crowded panel and need to orient the wiring access.
Switching capacity across the voltage range
Rated for 10 A at both 24 V and 230 V, which covers most control-circuit and small-load switching in a 24 VDC panel or a 230 VAC lighting/heater circuit. At 400 V it handles 3 A, and at 690 V it still switches 1 A — so it can handle contactor coil suppression or signal isolation in higher-voltage auxiliary circuits without derating to zero. The mechanical life is 30 million operations typical, and the arcing time sits between 10 and 15 ms — both figures that matter when you're counting cycles on a frequently cycled valve or conveyor interlock.
Panel fit and environmental limits
Dimensions are 73 mm deep × 45 mm wide × 70 mm tall — the 45 mm width is a single 9 mm module equivalent on a DIN rail, so it takes up one standard slot in a Siemens panel layout. Clearance to adjacent devices: 10 mm upwards, forwards, and downwards, and 6 mm at the sides — tight enough for dense layouts but you still need that breathing room for heat dissipation. Operates from -25 °C to +50 °C, stores from -55 °C to +80 °C, and is rated for pollution degree 3 — so it's fine in a typical industrial control cabinet, not a clean room.
Sourcing and lifecycle
RoHS compliance date is 10/01/2009, so it meets the EU substance restrictions for new installations.