Siemens 3RH1921-1HA22 Auxiliary Contact Block

Siemens 3RH1921-1HA22 is a four‑pole auxiliary contact block designed to mount on Sirius motor contactors (compatible with sizes S0 through S12) and provide two normally open and two normally closed contacts for control circuits. The block uses screw terminals for secure wiring and is specified to DIN EN 50012, making it suitable for signaling and interlock functions in industrial control systems. It features an insulation rating of 690 V and a surge withstand of 6 kV, enabling safe operation in common mains environments while isolating control circuitry from power contacts. The auxiliary contacts offer high mechanical life—up to 10,000,000 switching cycles—and electrical endurance rated as AC‑15 at 230 V, typically around 200,000 cycles, which supports frequent signaling in automated applications. Operating temperature up to +60°C is supported, and the unit is designed specifically for auxiliary signaling rather than power switching, helping to monitor coil status or provide PLC feedback. In use, it expands a contactor’s control capability by supplying both NO and NC feedback paths, enabling robust logic for interlocking, control logic, and safety circuits without compromising the primary switching of the motor load. The 3RH1921‑1HA22 is commonly referenced as a top-mounted, four‑pole auxiliary switch block for Siemens Sirius S‑series contactors, aligning with standard control‑circuit ratings and Siemens’ Sirius accessory ecosystem.