What it is and where it fits
The Siemens SIRIUS 3RH1921-2EA20-ZX95 is a first lateral auxiliary switch block that adds two normally-open (NO) contacts to a 3RT1 power contactor or contactor relay. It snaps onto the side of the contactor without tools, expanding the control circuit without increasing the panel's DIN-rail footprint. Rated for a maximum of 10 A, the switching capacity varies significantly with the applied DC voltage: 6 A at 24 V, 2 A at 60 V, 1 A at 110 V, 0.3 A at 220 V, and 3 A at 400 V. For AC applications, it handles 6 A at 230 V and 250 V. These are not continuous ratings — they define the make/break capability for the auxiliary contacts in a control circuit. The spring-loaded terminals accept 2x (0.5... 2.5 mm²) stranded without ferrules, or 2x (0.5... 1.5 mm²) with core-end processing. AWG 20 to 14 for the auxiliary wiring. This is a tool-less connection — strip, insert, spring clamps it — which speeds panel wiring and eliminates screw-torque checks.
Switching performance and durability
Mechanical service life is rated at 10,000,000 switching cycles typical. Contact reliability is specified as one faulty switching per 100 million operations at 17 V, 1 mA — a low-level signal test that matters for PLC inputs and safety circuits where dry switching can cause oxide film issues. Surge voltage resistance is 6 kV, and the insulation voltage at pollution degree 3 is 500 V AC. The IP20 protection on the front means it's protected against finger contact but not moisture — standard for a control-panel component inside an IP54 or higher enclosure. Operating temperature range is -25 to +60 °C; storage range extends from -55 to +80 °C. The storage limit governs handling and shipping, not running conditions.
Lifecycle and sourcing
The 3RH1921-2EA20-ZX95 is an active product in the Siemens SIRIUS line. No end-of-life notice or successor has been issued. It is sourced and quoted to order against an RFQ through independent distribution; availability and current pricing are confirmed at quote time.