The Siemens 3RH2911-4HA22 is a SIRIUS auxiliary switch block with two normally-open instantaneous contacts, designed to snap onto the front of contactor relays and power contactors in sizes S00, S0, S2, and S3. The 6 kV surge voltage resistance means it handles transient spikes common on industrial control circuits without failing.
Switching capacity — what the voltage columns mean
This block carries two sets of current ratings: the 'at X V' values (–) are the rated operational current for that voltage under the applicable utilization category, and the 'at X V rated value' entries (–) are the maximum thermal current at those voltages. At 24 V it switches 6 A with a rated thermal current of 10 A; at 230 V it still handles 6 A. At higher voltages the current drops — 3 A at 400 V, 0.26 A at 600 V. For AC-12 resistive loads the max is 10 A; for AC-15 at 690 V it's 1 A. That means for a typical 24 VDC control circuit you have headroom to 6 A, but if you're switching a 400 VAC pilot light the contact rating drops to 3 A. The mirror contact feature, compliant with IEC 60947-4-1, is only guaranteed when paired with a 3RT2 contactor — important for safety circuits where you need to verify the main contact state.
Dimensions: 36 mm wide, 43.7 mm deep, 37.5 mm tall. The snap-on mounting clips directly onto the contactor front without tools — no DIN rail required. The ring terminal lug connection means you'll need crimp ring terminals; no cage clamp or screw-cage here. The IP00 front means no ingress protection — keep it inside a sealed enclosure if there's dust or moisture.