The Siemens 3RH2140-2LB40 is a SIRIUS coupling relay sized S00, designed for switching auxiliary circuits in control panels. It carries 4 instantaneous N/O contacts and a 24 V DC coil rated at 2.8 W closing power, with a built-in varistor surge suppressor across the coil. This makes it straightforward to fit into tight panel layouts or retrofit into existing SIRIUS contactor assemblies.
At 400 V AC it's rated 3 A, and at 690 V AC it's 1 A — these numbers matter when switching contactor coils or signal lamps fed from different line voltages. Mechanical endurance is 30 million operations typical. Electrical life at AC is 10,000 operations per hour. For DC circuits, ensure the load time constant doesn't exceed these windows to avoid contact welding.
RoHS compliance date is 2009-10-01, covering the EU RoHS directive. The varistor surge suppressor is integrated — no external snubber needed for most inductive loads.