What it is and where it lands
The Siemens 3RH2140-1JB40 is a SIRIUS coupling relay — size S00 — designed for switching auxiliary circuits in control panels. It carries 4 normally-open instantaneous contacts rated 10 A at 24 V, with a 24 VDC coil drawing 2.8 W closing power. The built-in diode surge suppressor handles the inductive kick from the coil, so you don't need an external flyback diode across the PLC output. Mounting is screw-fix or snap-on onto standard 35 mm DIN rail. The S00 footprint — 45 mm wide, 57.5 mm tall, 73 mm deep — fits alongside contactors in a crowded panel. Clearance distances: 10 mm upward/downward/forward, 6 mm at the sides. Mounting position allows ±180° rotation on a vertical surface and ±22.5° tilt forward/backward, so it adapts to tight enclosures.
Ratings that govern the fit
The 4 NO contacts are rated for switching at multiple voltage levels: 10 A at 24 V and 230 V, 4.7 A at 60 V, 3 A at 110 V and 400 V, 1.2 A at 220 V, 0.5 A at 440 V, 2 A at 500 V, 0.26 A at 600 V, and 1 A at 690 V. That voltage-dependent derating is typical for DC switching — the arc extinguishes differently at higher voltages, so the contact rating drops. For a 24 VDC PLC output driving a valve or contactor coil, the 10 A rating gives generous headroom. Mechanical endurance is 30 million operating cycles typical. Electrical switching frequency at AC is 10,000 operations per hour; at DC the arcing time runs 10–15 ms with a switching interval of 38–65 ms.
Panel integration notes
Wire termination: spring-cage terminals accept 2x (0.5–1.5 mm²), 2x (0.75–2.5 mm²), or 2x 4 mm² solid or stranded. The S00 size shares the same DIN-rail footprint as Siemens contactors — you can gang them side-by-side without extra spacing beyond the 6 mm side clearance.