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. The AC-15 rating at 690 V (1 A) confirms it can switch solenoid loads in higher-voltage control schemes.
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. 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. Mechanical service life is 10 million switching cycles typical.