What this front-mounted auxiliary switch does
The 3RH2911-1LA20-ZW98 is a SIRIUS auxiliary switch block that snaps onto the front of Siemens 3RT2 contactors and 3RH2 contactor relays, adding two normally-open signal contacts (73/74, 83/84) for feedback or interlocking. Rated 10 A maximum, with AC-15 current ratings that drop as voltage rises: 6 A at 24 V, 3 A at 110 V, 1.2 A at 220 V, and 0.5 A at 440 V — the 690 V AC-15 rating is 1 A, which governs the contact life in high-voltage control circuits. Contact reliability is specified at one faulty switching per 100 million operations at 17 V, 1 mA — that covers dry-contact PLC inputs where the load current is well below the rated thermal current.
Snap-on fit and wiring for panel integration
Snap-on mounting to the contactor front face — no DIN-rail slot consumed. Dimensions are 36 mm wide, 37.5 mm tall, 43.7 mm deep, which keeps the assembly within the contactor envelope. Screw-type terminals accept 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²) per clamp, or 2x (20 to 16 AWG) and 2x (18 to 14 AWG). Cable entry from the top — plan wire routing above the contactor. IP20 on the front face means finger-safe in the enclosure but not washdown-rated. Rated insulation voltage is 690 V AC at pollution degree 3, with a 6 kV surge voltage resistance — suitable for 400 V line-to-line control panels with adequate clearance.
Sourcing and lifecycle for this SIRIUS auxiliary
No direct second-source cross-reference — the 3RH2 family is Siemens-specific for the 3RT2 contactor platform. Mechanical service life is 10 million switching cycles typical — that's a long-term spare for a contactor that cycles infrequently (valve control, conveyor interlock). The 2 NO contacts are independent; leading and lagging contact timing is not specified (both marked 0), so they switch simultaneously.