The Siemens SIRIUS 3RV1901-2F is a transverse auxiliary switch that mounts on the front of select SIRIUS circuit breakers (sizes S00, S0, S2, S3) to provide two normally-open (NO) instantaneous auxiliary contacts. It uses spring-loaded terminals — no screwdriver needed for the control wiring — accepting solid conductors from 0.5 to 2.5 mm² and stranded with ferrule from 0.5 to 1.5 mm². The contact rating is 2.5 A maximum; at 24 V it switches 1 A, at 48 V 0.3 A, at 60 V 0.15 A, and at 230 V 0.5 A.
The 3RV1901-2F is a phased-out product. The manufacturer lists a direct successor: the SIRIUS 3RV2 family, preferred successor type 3RV2901-2F. If you have this order code in a BOM or a panel drawing, the 3RV2901-2F is the official drop-in replacement to spec for new builds.
The switch plugs into the front of the breaker — no DIN-rail space consumed beyond the breaker itself. It is designed for the SIRIUS 3RV1 and compatible 3RV2 series breakers in sizes S00, S0, S2, and S3. The spring-loaded terminals accept the same wire ranges as the breaker's auxiliary circuit, keeping the wiring consistent across the panel.
The 2.5 A maximum is the total switching capacity across the two NO contacts — not per contact. Derate for inductive loads: the listed values at 24 V (1 A), 48 V (0.3 A), 60 V (0.15 A), and 230 V (0.5 A) are the actual switching limits at those voltages, so match the auxiliary load to the curve. The spring-loaded terminals (cage-clamp style) are fast to wire and vibration-resistant, common in panel builds where maintenance access is tight.