What it is and what it fits
The Siemens 3RH2911-1GA04-ZX95 is a front-mounted auxiliary switch block for the SIRIUS contactor relay family. It carries four normally-closed (NC) contacts, wired via screw-type terminals, and snaps onto the front of a contactor relay without tools. This block is physically coded and fits only the 3RH2140 and 3RH2440 contactor relays per EN 50011. It does not mount on other 3RH2 frames or on the 3RT series contactors.
Contact ratings and what they mean for your circuit
Each NC contact is rated for a maximum thermal current of 10 A. At 24 V the switching capacity is 6 A; at 230 V it is also 6 A, and at 400 V it drops to 3 A. For DC switching, the 24 V rating is 10 A, falling to 0.26 A at 600 V. The AC-15 rating at 690 V is 1 A, which governs the inductive load capability for solenoid and contactor coils at higher voltages. The insulation voltage is rated 690 V at pollution degree 3, with a surge voltage resistance of 6 kV. Contact reliability is specified at 1 faulty switching per 100 million operations at 17 V, 1 mA — a dry-circuit rating that confirms the contacts handle low-energy signals without oxidation issues.
Mechanical and environmental limits
The switch block measures 36 mm wide, 37.5 mm high, and 43.7 mm deep. It operates from -25 °C to +60 °C and can be stored from -55 °C to +80 °C. Front protection class is IP20. Mechanical service life is rated at 10 million switching cycles typical. Wire capacity accepts 2x (0.5 to 1.5 mm²) and 2x (0.75 to 2.5 mm²) with ferrule, or 2x (20 to 16 AWG) and 2x (18 to 14 AWG) for solid wire.