What it is and where it fits
The Siemens 3RH1921-2FA22-ZW96 is a SIRIUS auxiliary switch block with 2 normally-open and 2 normally-closed contacts, wired via spring-loaded terminals. It snaps onto contactor sizes S0 through S12, adding four auxiliary poles to a contactor relay or motor contactor. The "with 3RT1" note on the spec line means this block is designed to mount directly alongside the 3RT1 contactor family. Rated at 10 A at 24 V DC and 6 A at 230 V AC, the contacts handle typical control-circuit loads — PLC outputs, relay coils, indicator lamps. The AC-15 rating at 690 V (1 A) confirms it can switch solenoid loads in higher-voltage control schemes. Contact reliability is spec'd at one faulty switching per 100 million operations at 17 V, 1 mA, which matters for low-energy signal circuits where oxide films on dry contacts can cause intermittents.
Lifecycle and sourcing reality
This part is a phased-out product. The official successor is the SIRIUS 3RH2 series. For a BOM line that currently specifies 3RH1921-2FA22-ZW96, the replacement path is the 3RH2 auxiliary contactor block — but verify the mounting interface and terminal layout, since the 3RH2 series uses a different housing depth (73 mm vs. 51 mm) and width (45 mm vs. 44 mm), so a panel re-drill or adapter bracket may be needed. Sourcing is through independent distribution channels. Availability and current pricing are confirmed at quote time against an RFQ. No last-time-buy window is in effect from the manufacturer, so the surplus channel is the practical supply route for this order code.
Integration notes
Snap-on mounting onto a contactor — no screws, no DIN rail. The block occupies 44 mm width, 51 mm depth, and 38 mm height. Spring-loaded terminals accept 2x (0.5 to 2.5 mm²) without ferrules, or 2x (0.5 to 1.5 mm²) with core-end processing. AWG range is 2x (20 to 14). The IP20 front protection is standard for enclosed panel gear — no washdown rating here. Insulation voltage is 690 V AC at pollution degree 3, with a surge voltage resistance of 6 kV. That covers 480 V and 600 V control circuits with margin. Operating temperature range is -25 to +60 °C; storage range is -55 to +80 °C. Mechanical service life is 10 million switching cycles typical.