The Siemens 3RV2901-2F-ZX90 is a SIRIUS auxiliary switch designed as a transverse front-mount accessory for 3RV2 circuit breakers in sizes S00, S0, S2, and S3. It provides two normally open (NO) instantaneous contacts, with spring-loaded terminals for tool-free wiring.
The auxiliary contacts carry a maximum AC-12 rating of 2.5 A, but the real-world switching capacity depends on voltage: 1 A at 24 V, 0.3 A at 48 V, 0.15 A at 60 V, and 0.5 A at 230 V. These are the make-and-break limits for the contacts — if you're feeding a 24 VDC PLC input, you can pull the full 1 A through both NO contacts in parallel, but at 48 V you're limited to 0.3 A. The AC-12 rating (resistive load) is the ceiling; inductive loads like contactor coils or relay solenoids will need derating or a suppression network across the load.
Wiring and terminal specs
Spring-loaded terminals accept solid or stranded wire from 0.5 to 2.5 mm² (2x 0.5...2.5 mm² per clamp), or AWG 20 to 14. Finely stranded conductors with or without core-end processing are limited to 2x 0.5...1.5 mm². The plug-in fixing means the switch snaps onto the breaker without tools — no screws, no DIN rail slot consumed. This is a panel-builder's detail: the 17 mm depth keeps the assembly within the breaker's envelope, so you don't lose clearance to the enclosure door.