What it is and what it does
The Siemens 3RH1122-2VB40-ZX95 is a SIRIUS coupling relay designed for switching auxiliary circuits in control panels. It carries a 24 V DC coil with a rated operational current of 10 A at 24 V, making it suitable for pilot-duty and signal-level loads in motor control centers and PLC output interfaces. The relay is size S00, the smallest SIRIUS contactor footprint, and mounts via screw or snap-on to a DIN rail. Front-side protection is IP20, so it's intended for enclosed panel installation where personnel don't contact live parts.
Key ratings and what they mean for fit
The 24 V DC coil draws 1.4 W for both closing and holding, which is consistent across the SIRIUS S00 range. The built-in diode surge suppressor handles the inductive kickback, so you don't need an external flyback diode across the coil — verify polarity matches the diode orientation before wiring. Contact ratings are given per voltage: 10 A at 24 V, 6 A at 230 V, 3 A at 400 V, 2 A at 500 V, and 1 A at 690 V. For a 24 VDC control circuit, the full 10 A is available; at higher AC voltages the current derates due to arc extinction limits. The surge voltage resistance is rated at 6 kV, which covers most industrial transient environments without additional MOVs. Mechanical life is rated at 30 million operations typical, with contact reliability of one incorrect switching per 100 million operations at 17 V, 1 mA. That's a dry-circuit rating — it will switch low-level signals from sensors or PLC outputs without needing a minimum wetting current.
Mounting and environmental limits
The relay measures 45 mm wide, 60 mm high, and 73 mm deep. It can be mounted in any orientation: +/-180° rotation on a vertical surface, and tilted forward/backward by +/-22.5°. Operating temperature range is -25 to +60 °C; storage and transport range is -55 to +80 °C. Shock resistance is 10g for 5 ms and 5g for 10 ms. The screw terminals accept solid or stranded conductors from 0.25 to 2.5 mm² (2 x 2.5 mm² per clamp). Pollution degree 3 means it's rated for conductive pollution environments typical in industrial panels — no conformal coating required for normal use.