What this auxiliary switch does in the panel
The Siemens 3RH2911-1FB11-ZW97 is a front-mounted auxiliary switch block carrying one normally-open (leading) and one normally-closed (lagging) contact, rated for a maximum of 10 A. It snaps onto 3RT2 power contactors and 3RH2 contactor relays, adding feedback or interlock logic without extra wiring to the main power path. Rated operational current reaches 10 A at 24 V AC/DC, and the AC-15 switching category at 690 V is rated for 1 A — enough for pilot-duty control circuits on motor starters and valve actuators. Contact reliability is specified at one faulty switching per 100 million operations at 17 V, 1 mA, so it handles low-energy PLC inputs without nuisance failures.
Mounting and wiring constraints
Snap-on mounting to the contactor or relay front — no tools needed, but verify the latch engages fully before energizing. The screw-type terminals accept 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²) with core end processing, or AWG 20–16 and 18–14 for the auxiliary circuits. Dimensions are 36 mm wide, 37.5 mm tall, and 43.7 mm deep — it sits flush on the contactor face and does not increase the panel depth beyond the contactor body.