What it is and what it does
The Siemens SIRIUS 3RH1911-1GA31 is a 4-pole auxiliary switch block designed for use with SIRIUS contactor relays and power contactors. It provides 3 normally open (NO) and 1 normally closed (NC) instantaneous contacts, wired via screw-type terminals. The block snaps onto a 35 mm DIN rail per EN 50022, making it a straightforward add-on for expanding auxiliary contact capacity in a control panel. Rated at 10 A at 24 V, the contacts handle typical control-circuit loads — PLC inputs, pilot lights, relay coils — across a range of voltages. The AC-15 rating at 690 V is 1 A, which covers the inductive switching duty of contactor coils and solenoid valves in higher-voltage circuits.
Key ratings and what they mean for fit
The 10 A maximum at 24 V (and 6 A at 24 V for the auxiliary contact rating) means this block can switch multiple small loads in parallel without exceeding the contact current limit. The contact reliability spec — 1 faulty switching per 100 million operations at 17 V, 1 mA — confirms it handles dry circuits (low-current logic signals) reliably, which is critical for PLC input chains. Mechanical life is 10 million switching cycles typical, so in a machine cycling once every 10 seconds, the block outlasts about 3 years of continuous operation before mechanical wear becomes a concern. IP20 on the front means finger-safe from the panel face, but the block is not sealed against dust or moisture — it belongs inside a cabinet, not on a washdown line.
Integration in the panel
Snap-on mounting onto 35 mm DIN rail. Dimensions: 36.5 mm wide, 37.5 mm high, 41.5 mm deep — compact enough to fit alongside a contactor in a crowded gland plate. Wire termination accepts 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²) with core-end processing, or 2x (20–16) and 2x (18–14) AWG. Screw terminals are standard; no special tooling needed.