What it is — and what it does in a panel
The Siemens 3RH1131-1MB40 is a SIRIUS coupling relay built for switching auxiliary circuits in a control panel. Coil pulls in at 24 VDC, drops out at the lower end of the 0.85 to 2.15 range — standard for 24 V logic. Snaps onto a DIN rail or screws down; size S00 footprint (45 mm wide × 57.5 mm tall × 72 mm deep) fits tightly into a crowded enclosure. Three normally-open instantaneous contacts handle up to 10 A at 24 V, so it can drive a small contactor coil or indicator bank without an intermediate relay. Rated for pollution degree 3 and surge withstand up to 6 kV — typical for industrial panels where conductive dust or condensation is present. Contact reliability is quoted at one failure per 100 million operations at 17 V, 1 mA, which matters for PLC-level dry circuits.
Mounting and wiring details
Mounts on a vertical surface with screw or snap-on fastening. Can be rotated ±180° on that surface, and tilted forward or backward by ±22.5° — useful when a panel layout forces an odd angle. Wire terminations accept solid conductors: two of 0.5…1.5 mm², two of 0.75…2.5 mm², or one of 4 mm² per clamp. AWG equivalents are 20…16, 18…14, and 12 respectively. IP20 on the front — protected against finger contact, not washdown. Keep it inside the enclosure.