What it is and what it does
The Siemens 3RH1911-1FA31-ZW98 is a SIRIUS auxiliary switch block that snaps onto size S00 contactor relays and power contactors to add three normally-open and one normally-closed instantaneous contacts. It uses screw-type terminals and is rated for a maximum of 10 A, with contact reliability of one faulty switching per 100 million operations at 17 V and 1 mA. The 10 A rating applies across the contact set, but the actual switching capacity depends on the voltage and duty — at 24 V it carries 6 A in AC-15 service, while at 400 V the rating drops to 3 A.
Sourcing and lifecycle reality
This order code is a phased-out product according to the manufacturer, with the successor being the SIRIUS 3RH2 series.
Panel fit and integration
The block measures 36.5 mm wide, 37.5 mm high, and 41.5 mm deep, and snaps onto the front of a size S00 contactor — no additional DIN-rail space needed since it mounts directly on the contactor. Wiring accepts two conductors per terminal: 2x (0.5 to 1.5 mm²) and 2x (0.75 to 2.5 mm²) with ferrule, or 2x (20 to 16) and 2x (18 to 14) AWG. The front face carries an IP20 protection class, meaning it's protected against finger contact but not against moisture — suitable for enclosed control panels only.