What it is and what it does
The Siemens 3RH1131-2KV40 is a SIRIUS coupling relay, size S00, designed for switching auxiliary circuits in control panels. It provides 3 normally open instantaneous contacts, with a 36 V DC coil that draws 2.3 W for both closing and holding. Rated for 10 A at 24 V, the contacts handle the typical loads found in PLC output circuits, signal lamps, and small solenoid valves. The contact reliability spec — one incorrect switching operation per 100 million cycles at 17 V, 1 mA — confirms it is suited for low-level signal switching where oxidation on dry contacts is a concern. The built-in varistor surge suppressor protects the coil drive circuit from voltage spikes, which is relevant when the relay is driven by a solid-state output on a PLC or safety relay.
Where it fits in the panel
Mounts on a DIN rail via the screw and snap-on mechanism, occupying 45 mm width. The size S00 footprint is the smallest in the SIRIUS contactor family, so it fits in tight panel layouts where every millimeter counts. The mounting position is flexible — it can be rotated 180° on a vertical surface and tilted forward or backward by 22.5°, which helps when routing wires in a dense cabinet. The spring-cage terminals accept 0.25 to 2.5 mm² solid or stranded wire. Strip length is standard for this terminal family. The IP20 protection on the front means it is safe for finger contact inside an enclosure, but it is not rated for washdown or outdoor exposure.
Key ratings and their meaning
The rated surge voltage resistance of 6 kV ensures the relay withstands transient overvoltages common in industrial control panels without flashover or insulation breakdown. Pollution degree 3 means it is designed for the conductive pollution environment typical of factory floors — no special conformal coating required for normal use. The thermal and shock ratings — 10g for 5 ms and 5g for 10 ms — cover the vibration found on machine-mounted panels or near heavy rotating equipment. The operating temperature range of -25 to +60 °C is standard for industrial control gear, while the storage range of -55 to +80 °C covers transport and warehouse conditions. The contacts are rated for switching at various voltages: 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 thermal current ratings for the auxiliary contacts — they define the maximum continuous current the contacts can carry, not the motor starting current.