What This Auxiliary Switch Does on a Contactor
The 3RH2911-2HA02-ZX95 is a front-mounted auxiliary switch block for Siemens SIRIUS 3RT2 contactors and 3RH2 contactor relays — it adds two normally-closed (NC) signal paths to the base device without expanding the panel footprint. Rated 10 A maximum, with a rated current that varies by voltage: 10 A at 24 V, 4.7 A at 60 V, 3 A at 110 V, 1.2 A at 220 V, 0.5 A at 440 V, and 0.26 A at 600 V. The AC-15 rating at 690 V is 1 A — that is the switching capacity for inductive loads like contactor coils or solenoid valves in a control circuit. The insulation voltage is 690 V at pollution degree 3, and surge voltage resistance is 6 kV — this means the switch is rated for use in industrial environments with moderate conductive contamination, and it can withstand transient overvoltages common in motor control panels.
Snap-On Mounting and Terminal Specs
Fastens by snap-on mounting directly to the front of the contactor or relay — no tools or DIN rail required. Dimensions: 36 mm wide, 47.7 mm deep, 41.5 mm high. Spring-loaded terminals accept two conductors per clamp: 2x (0.5…1.5 mm²) with ferrule or 2x (0.5…2.5 mm²) without, and 2x (20…14 AWG). The spring-clamp design speeds wiring — strip, push, done — and holds under vibration. The front protection class is IP20 — finger-safe but not sealed; the switch is intended for use inside a panel enclosure with a higher overall IP rating.
Contact Configuration and Reliability
Two NC contacts, both wired as normally-closed — the current path is 1 NC, 1 NC. The leading and lagging switching contacts are both listed as 0, meaning no make-before-break or break-before-make sequencing; both NC paths open simultaneously. Contact reliability is specified as 1 faulty switching per 100 million operations at 17 V, 1 mA — this is the low-energy switching limit, important for PLC input circuits where dry-contact signals must not bounce or fail to close. Mechanical service life is 10 million switching cycles typical — the switch outlasts most contactor main contacts under normal control duty.