The Siemens SIRIUS 3RH1911-1GA40-ZW98 is a 4-pole auxiliary switch block with 4 normally-open contacts (40 E per EN 50011), designed for snap-on mounting onto contactor relays and power contactors in the SIRIUS family. It uses screw-type terminals and carries a maximum thermal current rating of 10 A, with contact reliability rated at 1 faulty switching per 100 million operations at 17 V, 1 mA — a figure that matters for low-signal PLC input circuits where a single false closure can cause a misread.
Lifecycle and replacement path
This order code is a phased-out product. The manufacturer lists the successor as the SIRIUS 3RH2 series — a form-fit-function evolution that maintains the same 4-pole auxiliary contact arrangement but updates the platform. For a BOM line frozen around the 3RH1911 footprint, the 3RH2 block is the direct drop-in replacement candidate to validate against the existing panel layout and wire lengths.
Ratings and what they mean for fit
The 4 NO contacts (40 E) suit applications requiring multiple isolated feedback signals from a single contactor — for example, sending one pair to the PLC input card and another to a hardwired safety circuit. The 10 A maximum thermal current covers most control-circuit loads, but the switching capacity varies significantly by voltage: at 24 V DC it handles 6 A (resistive), while at 220 V AC it drops to 0.3 A. The AC-15 rating at 690 V is 1 A, confirming this block is intended for auxiliary switching of contactor coils, solenoid valves, and indicator lamps — not motor loads. Insulation voltage is 690 V with pollution degree 3, and surge voltage resistance is 6 kV, which keeps the block reliable in industrial panels without additional suppression on the auxiliary circuit.
Mounting and wiring
Snap-on mounting onto a 35 mm DIN rail or directly onto a SIRIUS contactor relay. The screw terminals accept 2x (0.5 to 1.5 mm²) and 2x (0.75 to 2.5 mm²) with core-end processing, or 2x (20 to 16) and 2x (18 to 14) AWG. Dimensions are 36.5 mm wide, 37.5 mm high, and 41.5 mm deep — compact enough for dense panel layouts. Front protection is IP20; the block is rated for operation from -25 °C to +60 °C and storage from -55 °C to +80 °C.