What This Part Is and Where It Fits
The Siemens SIRIUS 3RH1921-2FA11 is an auxiliary switch block providing one normally-open and one normally-closed contact, wired via spring-loaded terminals. It snaps onto contactor relays and power contactors in the S0 through S12 frame sizes, per the EN 50005 mounting standard. The 'with 3RT1' note on the line item indicates this block is designed to pair with the 3RT1 contactor family — it's the add-on contact module, not a standalone contactor.
Key Ratings and What They Mean for Fit
The contacts are rated 10 A at 24 V under AC-15 duty, which covers solenoid and electromagnetic loads typical in control circuits. At 400 V the rating drops to 3 A, and at 690 V it's 1 A — the insulation voltage is rated 690 V with pollution degree 3, so this block can live in a standard industrial panel without extra creepage spacing. The mechanical service life is 10 million switching cycles, and the contact reliability spec calls out one faulty switching per 100 million operations at 17 V, 1 mA — a meaningful figure for PLC input circuits where dry switching can cause oxide buildup on standard contacts.
Physical Integration and Wiring
Dimensions are 44 mm wide, 38 mm high, and 51 mm deep — it occupies the same width as the S0 contactor it mounts on. The spring-loaded terminals accept 2x 0.5 to 2.5 mm² without ferrules, or 2x 0.5 to 1.5 mm² with ferrules. AWG equivalents are 2x 20 to 14. The front face carries IP20 protection, meaning finger-safe but not washdown-rated. Operating temperature range is -25 to +60 °C; storage range is -55 to +80 °C. Surge voltage resistance is 6 kV.