What it is — front-mounted auxiliary switch for SIRIUS contactors
The Siemens 3RH2911-1MA02 is a front-mounted auxiliary switch block for the SIRIUS family, designed to snap onto 3RT2 power contactors and 3RH2 contactor relays. It carries two normally-closed (NC) circuits — terminals 71/72 and 81/82 — with cable entry from below. The screw-type terminals accept 2x (0.5...1.5 mm²) or 2x (0.75...2.5 mm²) conductors, or 2x (20...16) or 2x (18...14) AWG.
Key ratings — what they mean for fit
Rated at 10 A thermal current (Ith), this block handles the full auxiliary contact rating of the contactor frame it mounts to. The AC-15 switching capacity tells you the real-world inductive load it can break: 10 A at 24 V, 6 A at 125/230/250 V, 3 A at 400 V, and 1 A at 690 V. For DC switching, the ratings drop faster — 6 A at 24 V, 2 A at 60 V, 1 A at 110 V, 0.3 A at 220 V — so check your DC control circuit voltage against the curve. The insulation voltage is 690 V at pollution degree 3, with a rated surge voltage resistance of 6 kV, meaning it's suitable for 400/480 VAC panels without additional creepage concerns. Contact reliability is specified at 1 faulty switching per 100 million operations at 17 V, 1 mA — a low-level signal rating that matters if you're routing PLC inputs through these contacts. Mechanical life is 10 million switching cycles typical, which outlasts most contactor main contacts in cyclic service.
Where it fits — panel integration
Snap-on mounting to the contactor front. Dimensions: 36 mm wide, 37.5 mm high, 43.7 mm deep. IP20 on the front. Operating temperature -25 to +60 °C, storage -55 to +80 °C.