The Siemens SIRIUS 3RV5901-1B is a lateral auxiliary switch designed to snap onto the side of SIRIUS circuit breakers in sizes S00, S0, S2, and S3. It provides two normally open (NO) instantaneous contacts for status feedback or control logic, wired via screw-type terminals accepting 2x (0.5...1.5 mm²) or 2x (0.75...2.5 mm²) solid or ferruled stranded conductors.
What the contact ratings mean for your circuit
The contact ratings are voltage-dependent, not a single blanket ampacity. At 24 V the switch is rated 2 A; at 230 V it handles 4 A; at 400 V it's 3 A; and at 690 V it reaches the maximum 10 A. The AC-15 rating at 690 V is 1 A, which governs inductive loads like contactor coils. This means the 3RV5901-1B can carry higher currents at higher voltages in resistive or lightly inductive circuits, but for heavily inductive switching (AC-15) you derate significantly at 690 V.
Panel fit and mounting
At 9.5 mm wide, this auxiliary switch adds minimal DIN-rail footprint when plugged into the side of the breaker. The plug-in fixing means no separate mounting hardware — it clips directly onto the breaker housing. Front touch protection is finger-safe per IEC 60529, with IP20 protection on the front face. Operating temperature range is -20 to +60 °C; storage range is -50 to +80 °C.