The Siemens SIRIUS 3RH2911-4GA31 is a front-mounted auxiliary switch block designed specifically for the 3RH2140 and 3RH2443 contactor relay frames. It provides 3 normally open and 1 normally closed instantaneous contacts, physically coded so it only mounts on those two base units — a detail that prevents misassembly on the wrong relay. The contact configuration is 53/54 (NO), 61/62 (NC), 73/74 (NO), 83/84 (NO).
The maximum continuous current is 10 A, but the real selection parameter is the voltage-specific switching capacity. For DC circuits the derating is steeper: 10 A at 24 V DC, 4.7 A at 60 V DC, 1.2 A at 220 V DC, and 0.26 A at 600 V DC. These are the values that govern whether the contacts survive the inrush and break the load without welding — the 10 A maximum is a thermal limit, not a universal switching rating. The AC-15 rating at 690 V is 1 A, which covers solenoid valve and electromagnetic brake loads at that voltage level. The insulation voltage is rated 690 V at pollution degree 3, and surge voltage resistance is 6 kV — both confirm the block is suitable for industrial environments where transient overvoltages are common.
Contact reliability and service life
Connection and wiring
Termination is via ring terminal lug connection — not screw terminals or spring cages. That means the installer needs to crimp ring lugs onto the control wiring before landing them on the block. The physical coding (a mechanical key) ensures the block only fits the intended 3RH2 base units, so a panel builder cannot accidentally install it on a different contactor relay family.