Auxiliary switch for S00 breakers — solder pin variant
The Siemens 3RV1918-5B is a SIRIUS auxiliary switch designed for the S00 frame size of the 3RV motor-protective circuit breaker family. It provides two normally-open (NO) instantaneous contacts via solder pin terminals — no screw-clamp wiring, so it mates directly to a PCB or a mating connector header inside the panel. Rated at 10 A maximum at 690 V AC, the contacts handle the signal-level switching common in control circuits — pilot devices, PLC inputs, contactor coils — not main motor current. The AC-15 rating at 690 V drops to 1 A, which is the inductive load limit for solenoid and contactor coils at that voltage.
Lifecycle and replacement path
For existing panels with the 3RV1 breaker family, this auxiliary switch remains a critical spare — one in the cabinet before it fails.
Clips onto the side of a 3RV1 S00 circuit breaker — no DIN rail space consumed, no extra wiring channel needed. The solder pins project downward; plan for a mating connector or PCB clearance below the breaker in the panel layout.