What It Is and What It Does
The Siemens SIRIUS 3RH2911-2GA04-ZW98 is a front-mounted auxiliary switch block designed for use with SIRIUS contactor relays. It provides four normally closed (NC) switching paths — contacts 51/52, 61/62, 71/72, and 81/82 — for status feedback, interlocking, or control logic in a motor starter or contactor assembly. Rated for a maximum thermal current of 10 A, it handles AC-15 pilot-duty loads up to 1 A at 690 V, and its AC-15 switching capacity at lower control voltages is substantial: 10 A at 24 V, 6 A at 125/230/250 V, and 3 A at 400 V. This makes it suitable for switching contactor coils, relays, and PLC inputs across common control voltages. The block snaps onto a DIN rail and is physically coded to mate only with SIRIUS contactor relays 3RH2140 and 3RH2440 per EN 50011, preventing misassembly. Spring-loaded terminals accept 2x (0.5 to 1.5 mm²) with ferrules or 2x (0.5 to 2.5 mm²) solid, and 2x (20 to 14 AWG) stranded.
Ratings That Matter for Fit
The AC-15 rating at 690 V (1 A) is the key figure for pilot-duty switching in 400/690 V industrial networks — it confirms the contacts can reliably switch inductive loads like contactor coils at that voltage without welding. The 6 kV rated surge voltage resistance means the insulation withstands transient overvoltages typical in industrial control panels. Contact reliability is specified at one faulty switching per 100 million operations at 17 V, 1 mA — a dry-circuit capability that matters for PLC input signals where low-energy switching must be consistent. The mechanical service life of 10 million switching cycles typical indicates a robust mechanism for high-duty applications. IP20 on the front means finger-safe from the panel face but not protected against moisture ingress — this is a dry indoor panel part. The operating temperature range of -25 to +60 °C covers most control cabinet environments; storage range extends to -55 to +80 °C.
Sourcing and Lifecycle
The multi-unit packaging (pack of 50) is the standard ordering quantity for this variant — the -ZW98 suffix denotes the bulk pack. For single-unit needs, the non-ZW98 version of the same switch block is the usual alternative, though the exact order code differs.