What this part is and what it does
The Siemens SIRIUS 3RH1911-1FA31-ZX95 is an auxiliary switch block that snaps onto size S00 contactor relays and power contactors, adding three normally-open and one normally-closed auxiliary contacts. It uses screw-type terminals and is rated for 10 A at 24 V, with a contact reliability of one incorrect switching operation per 100 million operations at 17 V, 5 mA. The front face carries IP20 protection, meaning it's safe from finger contact but not sealed against dust or moisture — standard for panel-mounted auxiliary blocks.
Lifecycle and sourcing reality
This part is a phased-out product. The manufacturer lists the successor as the SIRIUS 3RH2 series. For a BOM line that was specified around the 3RH1911-1FA31-ZX95, the 3RH2 is the official drop-in replacement path — but the physical footprint and terminal layout differ, so a panel re-qualification is needed before swapping. The 3RH1911-1FA31-ZX95 itself is sourced to order against an RFQ through independent distribution channels; availability and current pricing are confirmed at quote time.
Contact ratings — what they mean for your circuit
The 10 A maximum at 24 V is the thermal current rating (Ith) for the auxiliary contacts. The real-world switching capacity depends on voltage and load type: at 110 V it's rated 1 A, at 230 V it's 6 A, and at 400 V it drops to 3 A. For DC switching, the ratings are 6 A at 24 V, 2 A at 60 V, and 0.3 A at 220 V. These numbers govern whether the block can handle your specific pilot device or PLC input load — overshoot the voltage-specific rating and the contacts may weld or fail early.
Mechanical and environmental limits
Rated for 10 million mechanical switching cycles typical. Operating temperature range is -25 to +60 °C, storage from -55 to +80 °C. The insulation voltage is 690 V at pollution degree 3, with a surge voltage resistance of 6 kV. These specs mean the block is suited for industrial control panels in normal factory environments — not for outdoor or wet locations without additional enclosure protection.
Panel integration
Snap-on mounting onto size S00 contactors — no tools needed for attachment. Dimensions are 36.5 mm wide, 37.5 mm high, 41.5 mm deep. Wiring accepts 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²) with core-end processing, or 2x (20 to 16) and 2x (18 to 14) AWG. The screw terminals are standard for panel wiring; no special termination tools required.