The Siemens 3RH2140-2VB40 is a SIRIUS coupling relay for switching auxiliary circuits — the kind of part that sits between a PLC output and a contactor coil, or routes signals across a panel. Size S00 footprint (70 mm tall, 45 mm wide, 73 mm deep) with screw and snap-on mounting onto 35 mm DIN rail, so it drops into any standard enclosure rail without a sub-panel. Four NO instantaneous contacts, each rated 10 A at 24 V and at 230 V, give you enough switching capacity for multiple pilot loads or signal isolation. Coil is 24 VDC with a pickup threshold of 0.85 x rated (about 20.4 V) and a dropout of 1.85 x rated — meaning it holds in cleanly down to about 20 V and won't drop out on a sag to 18 V, but releases reliably when the control voltage goes above 44 V. Built-in diode surge suppressor across the coil, so you don't need an external flyback diode for inductive load switching. That saves a component and a wiring step at the panel.
Mounting and clearances
Mounts screw or snap-on onto 35 mm DIN rail. Position flexibility: ±180° rotation on a vertical surface, and can be tilted forward/backward by ±22.5° on vertical mount. Minimum clearances: 10 mm upwards, 10 mm forwards, 10 mm downwards, 6 mm at the side — tight enough for dense rail packing, but keep the 10 mm vertical gap for airflow and wiring access. Terminals accept 2 x (0.5 to 4 mm²) solid or stranded — screw-clamp, not push-in. Strip length is standard; torque to the usual 0.8–1.2 Nm range for this class. Ambient operation -25 to +50 °C, storage -55 to +80 °C, with 10% minimum relative humidity and pollution degree 3 (conductive or dry non-conductive with condensation). Fine for most industrial control panels, including non-climate-controlled cabinets.
Switching performance and contact ratings
Rated operational current across the voltage range: 10 A at 24 V, 10 A at 230 V, 4.7 A at 60 V, 3 A at 110 V, 1.2 A at 220 V, 3 A at 400 V, 0.5 A at 440 V, 2 A at 500 V, 0.26 A at 600 V, 1 A at 690 V. That's a wide AC/DC coverage — the 10 A at 230 V is the headline figure for most 24 V and 230 V pilot circuits. Mechanical endurance: 30 million operating cycles typical. Electrical endurance at AC: 10,000 operations per hour; at DC: 20 to 80 ms arcing time per operation. Arcing time is 10 to 15 ms — fast enough for most auxiliary switching, but watch the DC load breaking at higher voltages where the arcing time stretches. Coil power consumption at DC: 1.6 W closing power — low enough to drive from a standard 24 VDC PLC output without an interposing relay in most cases. No auxiliary switch extension on this variant; it's a straight 4 NO contact block.