What it is and where it fits
The Siemens 3RH2911-1GA22-ZW98 is a SIRIUS auxiliary switch block designed exclusively for the 3RH2140 and 3RH2440 contactor relay frames. It provides 2 normally-open and 2 normally-closed contacts arranged per EN 50011, with screw-type terminals for the auxiliary and control circuits. The physical coding on the housing prevents accidental mounting on incompatible relay bases — it only clicks onto those two specific relay models.
Switching ratings — what they mean for your control circuit
Rated for 10 A maximum, with AC-15 switching capacity at 24 V also rated at 10 A. That means it handles the inrush of contactor coils and solenoid valves in a control panel without welding the contacts. At higher voltages the current capability drops — 6 A at 230 V, 3 A at 400 V, and 0.5 A at 440 V — so verify your load's voltage before committing the BOM line. The surge voltage resistance is rated at 6 kV, which covers most industrial distribution transients without additional suppression.
Mechanical and environmental limits
Rated for 10 million mechanical switching cycles typical, so it outlasts most contactor relays in cyclic service. Operating temperature range is -25 to +60 °C, storage from -55 to +80 °C. The IP20 front protection means it's intended for enclosure interior use only — no washdown or outdoor exposure without a secondary cover.
Mounting and wiring
Snap-on mounting to the relay base — no DIN rail footprint of its own, it rides on the contactor relay. Screw terminals accept 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 contact reliability spec — one faulty switching per 100 million operations at 17 V, 1 mA — confirms it handles dry circuits (low-voltage logic signals) without needing gold-plated contacts.