What it is and what it does
The Siemens 3RH1911-1FA31-ZW97 is a SIRIUS auxiliary switch block designed for use with contactor relays and power contactors in the S00 frame size. It provides 3 normally open (NO) and 1 normally closed (NC) contact configuration per EN 50005, wired via screw-type terminals. The block snaps onto the contactor without tools, adding auxiliary contacts for status feedback, interlocking, or control logic extension.
Key ratings and what they mean for fit
Rated at 10 A maximum, with derated currents per voltage level: 6 A at 24 V, 6 A at 125 V, 6 A at 230 V, and 3 A at 400 V. The AC-15 rating at 690 V is 1 A, which governs switching of electromagnetic loads like contactor coils in higher-voltage control circuits. The insulation voltage is 690 V at pollution degree 3, and surge voltage resistance is 6 kV — adequate for industrial control panels with standard overvoltage category III. Mechanical service life is 10 million switching cycles typical. Contact reliability is specified as 1 faulty switching per 100 million operations at 17 V, 1 mA — a low-level switching spec that matters for PLC input circuits where dry-contact signals must be reliable.
Physical integration and environment
Dimensions: 36.5 mm wide, 37.5 mm high, 41.5 mm deep. Snap-on mounting to the contactor — no DIN rail required for the block itself, though the contactor typically mounts on a 35 mm rail. IP20 protection on the front, suitable for enclosed panel use. Operating temperature range -25 to +60 °C; storage range -55 to +80 °C. 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.