What it is and what it does
The Siemens 3RH1122-2KJ80 is a SIRIUS coupling relay — a size S00 auxiliary contactor designed for switching auxiliary circuits in control panels. It carries 2 normally-open instantaneous contacts and no normally-closed or delayed contacts, so it's a straight-forward on/off signal repeater. The 72 V DC coil draws 2.3 W for both closing and holding, and includes a built-in varistor surge suppressor. That means no external flyback diode needed — the varistor clamps the inductive kick when the coil de-energizes, which simplifies panel wiring and protects nearby electronics.
Key ratings — what they mean for fit
Rated switching currents are specified by 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. These are the maximum continuous currents the contacts can make and break under AC loads — match them against your auxiliary circuit's draw, not the main motor current. Contact reliability is rated at one incorrect switching operation per 100 million cycles at 17 V, 1 mA. That's a dry-circuit spec — important if this relay is switching low-level signals like PLC inputs or sensor feedback where oxide films on standard contacts can cause intermittent failures. Surge voltage resistance is 6 kV, and pollution degree is 3 (conductive pollution or dry non-conductive pollution that becomes conductive due to condensation). This means the relay is suited for industrial environments where transient spikes and airborne contaminants are normal — typical for motor control centers and production line panels.
Mounting and integration
Mounts via screw or snap-on onto a DIN rail. The size S00 footprint — 45 mm wide, 60 mm tall, 73 mm deep — fits the standard S00 contactor slot in a Siemens SIRIUS panel layout. Mounting position is flexible: +/-180° rotation on a vertical surface, plus +/-22.5° tilt forward/backward. Terminals accept solid conductors from 0.25 to 2.5 mm² (2x per clamp). IP20 on the front means finger-safe but not washdown-rated — keep it inside the enclosure, not on the machine frame.
Lifecycle and sourcing
RoHS compliance date is July 1, 2006, covering the standard EU substance restrictions. No separate UL or CSA listing appears in the spec record, but the SIRIUS family typically carries those approvals — verify against your local panel certification requirements.