What it is and what it does
The Siemens SIRIUS 3RH1911-2GA31 is a 4-pole auxiliary switch block with a 3 NO + 1 NC contact arrangement per EN 50011, designed for snap-on mounting onto contactor relays and power contactors in the SIRIUS family. Rated at 10 A maximum, the contact ratings vary significantly by voltage and duty: at 24 V it carries 10 A (or 6 A depending on the duty class), at 230 V it carries 6 A, and at 400 V it drops to 3 A — the AC-15 rating at 690 V is 1 A, which governs its use in solenoid and contactor coil switching circuits. Spring-loaded terminals accept 2x (0.5 to 1.5 mm²) with ferrules or 2x (0.5 to 2.5 mm²) solid, saving panel wiring time compared to screw terminals.
Where it fits and what it connects to
Snap-on mounting to a 35 mm DIN rail or directly onto a SIRIUS contactor relay — the 46 mm depth, 36.5 mm width, and 37.5 mm height mean it adds minimal footprint to the contactor stack. IP20 on the front means it is protected against finger contact but not washdown; it belongs inside a panel or enclosure, not on an exposed machine frame. Insulation voltage rated at 690 V AC with pollution degree 3 and surge voltage resistance of 6 kV — suitable for 400 V line-to-line industrial panels with standard clearance spacing.
Contact reliability and mechanical endurance
Mechanical service life is 10 million switching cycles typical. Contact reliability is rated at 1 faulty switching per 100 million operations at 17 V, 1 mA — meaning it handles dry-circuit (low-energy) signals in PLC inputs or safety circuits without the contact oxidation problems that plague general-purpose relays.