Front-mounted auxiliary switch for 3RH2 and 3RT2
The 3RH2911-1FA40-ZW96 is a front-mounted auxiliary switch block from the Siemens SIRIUS family, designed to snap onto 3RH2 contactor relays and 3RT2 power contactors. The note 'with 3RH2' confirms the mechanical interface — this block mounts directly on the front of the relay, adding four normally open (4 NO) instantaneous contacts without increasing the panel footprint beyond the base device. Rated operational current in AC-15 duty (solenoid and contactor coil switching) is 10 A at 24 V, 6 A at 230 V, and 3 A at 400 V. These ratings define the inductive load switching capability — the 10 A at 24 V is the headline figure for typical 24 VDC control circuits, while the 3 A at 400 V covers line-voltage coil applications. Contact reliability is specified at 1 faulty switching per 100 million operations at 17 V, 1 mA, meaning this block handles low-level signal switching (e.g., PLC inputs) without the contact oxidation problems that plague standard power contacts at dry-circuit levels.
DIN rail snap-on and wiring constraints
Fastening is snap-on mounting to a standard DIN rail — no tools needed for installation, but the block must be positioned on the rail before the base contactor or relay is wired. Dimensions are 36 mm wide, 43.7 mm deep, and 37.5 mm high, so it adds minimal depth to the assembly. Screw-type terminals accept 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²) conductors with core end processing, or 2x (20 to 16) and 2x (18 to 14) AWG. The dual-conductor capacity per terminal is useful for daisy-chaining control wiring without additional junction points. Front protection class is IP20 — finger-safe but not sealed against dust or moisture. The block is intended for use inside a control cabinet rated to at least IP54; it is not suitable for washdown or outdoor exposure without an enclosure.
Active production and sourcing posture
Mechanical service life is 10 million switching cycles typical, which suits high-cycle applications like conveyor interlocking or machine tool sequences where the auxiliary contacts see frequent operation. Insulation voltage is 690 V AC at pollution degree 3, with a rated surge voltage resistance of 6 kV. This means the block is coordinated for use in industrial panels where transient overvoltages from motor switching or lightning-induced surges are present, without requiring additional surge suppression on the auxiliary circuit.