What it is and where it fits
The Siemens 3RV6901-1B is a lateral auxiliary switch from the SIRIUS family, designed to snap onto the side of SIRIUS circuit breakers in sizes S00, S0, S2, and S3. It adds two normally-open (2 NO) instantaneous contacts to the breaker, letting you pick off a status signal or interlock a control circuit without a separate contactor.
Contact ratings — what the numbers mean for your circuit
The 2 NO contacts carry a range of voltage-specific current ratings that reflect real switching duty, not just a single thermal current. At 24 V it switches 2 A; at 110 V it drops to 0.5 A; at 220 V it handles 0.25 A. For higher-voltage control circuits, the AC-12 maximum is 10 A at 230 V, and the AC-15 rating at 690 V is 1 A — the latter is the one to check if you're switching an inductive contactor coil at line voltage. The 690 V 10 A entry likely reflects the AC-12 resistive load ceiling at that voltage, while the 400 V 3 A sits between typical motor-control voltages.
Panel fit and wiring
At 9.5 mm wide and 70 mm deep, this switch adds minimal DIN-rail real estate — about one-third the width of a standard S00 contactor. The screw-type terminals accept 0.5 to 2.5 mm² solid or stranded wire (2x 0.5…1.5 mm² or 2x 0.75…2.5 mm² per clamp), which covers the common control-circuit wire sizes in a panel. AWG 20 to 14 is the coded range for the auxiliary contact terminals. The plug-in fixing means it clips directly to the breaker body without extra hardware.
Compliance documentation
The substance prohibitance date is 05/01/2012.