What it is and what it does
The Siemens 3RH1122-2JC40-ZW95 is a SIRIUS coupling relay — essentially a contactor-sized auxiliary relay for switching control circuits, not motor loads. It carries 2 NO (instantaneous) contacts, each rated 10 A at 24 V, and is built into the S00 contactor frame size (45 mm wide, 60 mm tall, 73 mm deep). The 10 A at 24 V rating means it can handle the full coil inrush of multiple small contactors or a bank of solenoid valves without derating. For higher-voltage control circuits, the current drops: 6 A at 230 V, 3 A at 400 V, 1 A at 690 V — the typical AC-15 / DC-13 auxiliary contact curve for a relay of this size.
Mounting and panel integration
Mounts via screw or snap-on to a DIN rail. The S00 footprint — 45 mm wide — is the smallest Siemens contactor frame, so it fits in tight panel layouts. Mounting position allows +/-180° rotation on a vertical surface and +/-22.5° tilt forward/backward, useful when the relay sits on a swing frame or door. Terminals accept solid or ferruled stranded wire 0.25 to 2.5 mm². IP20 on the front face means it's protected against finger contact but not washdown — standard for an enclosed panel relay.
Compliance and environmental
RoHS compliant per the substance prohibition date of July 1, 2006. The built-in surge suppressor is a diode — verify polarity if the control circuit uses DC switching, because a diode clamps the reverse voltage but blocks one half-cycle on AC. Rated surge voltage resistance is 6 kV (pollution degree 3), meaning it's suitable for industrial environments where transients from contactor coils or motor starts are common. Mechanical life is 30 million operations; contact reliability is rated at 1 incorrect switching per 100 million operations at 17 V, 1 mA — a dry-circuit spec that matters for PLC input signals.