What it is and what it fits
The Siemens SIRIUS 3RH1911-1NF20 is an auxiliary switch block designed for use with contactor relays and power contactors in the S00 frame size. It provides 2 normally open (NO) instantaneous contacts, wired via screw-type terminals. Snap-on mounting onto a 35 mm DIN rail makes it a straightforward addition to a control panel, adding auxiliary contacts without increasing the contactor's footprint beyond the S00 envelope. The 41.5 mm depth, 36.5 mm width, and 37.5 mm height keep it compact for tight enclosures.
Key ratings and what they mean for fit
Rated insulation voltage of 690 V at pollution degree 3 means the block is suitable for 400 V and 480 V line-to-line control circuits common in industrial panels, with adequate creepage for dusty or conductive environments. Surge voltage resistance of 6 kV covers typical transient overvoltages in industrial mains. The auxiliary contacts are rated at 0.3 A at both 24 V and 60 V — this is a low-current, signal-level rating intended for PLC inputs, contactor coils, or indicator lamps, not for power switching. Contact reliability is specified at 1 faulty switching per 100 million operations at 17 V and 1 mA, confirming suitability for electronic control circuits where false signals are costly. Mechanical service life of 5 million operating cycles is typical for this class of auxiliary block in a contactor application, matching the expected life of the base contactor in moderate-duty cycling. IP20 protection on the front means the block is protected against finger contact but not against moisture ingress — it belongs inside a sealed enclosure, not in a washdown zone.
Lifecycle and sourcing reality
This part is flagged as a phased-out product. The official Siemens successor is the SIRIUS 3RH2911-1NF20, which is the preferred replacement. For BOM lines still specifying the 3RH1911-1NF20, sourcing is through the surplus and broker channel — quoted to order against an RFQ. The successor shares the same S00 footprint, 2 NO contact arrangement, and screw terminal connection, so a panel designed for the 3RH1911 can typically accept the 3RH2911 without rewiring, but verify the mounting rail and wiring space match.
Wiring and terminal details
Screw-type terminals accept 2 conductors per clamp: 0.5 to 1.5 mm² or 0.75 to 2.5 mm² with core end processing, or 20 to 16 AWG and 18 to 14 AWG respectively. This covers standard control wiring for auxiliary circuits. Operating temperature range is -25 to +60 °C, with storage from -55 to +80 °C.