What it is and what it does
The Siemens SIRIUS 3RH1122-2BM40 is an auxiliary contactor in size S00, designed to switch control signals and low-power loads in motor control centers and industrial panels. It provides two normally open instantaneous contacts, rated for 10 A at 24 V and 6 A at 230 V, with a surge voltage resistance of 6 kV. Rated for pollution degree 3, it suits environments with conductive contamination. Snap-on mounting onto a DIN rail or screw fixing is supported, with a mounting position that allows ±180° rotation on a vertical surface and ±22.5° tilt forward/backward. This flexibility simplifies integration into existing panel layouts where space or orientation is constrained.
Key ratings and what they mean for fit
The 10 A rating at 24 V DC covers typical PLC digital output loads and relay coils. At 230 V AC the contactor handles 6 A, enough for small solenoid valves or indicator circuits. The 6 kV surge voltage rating means it withstands switching transients common in industrial environments without contact welding or insulation breakdown. Contact reliability is specified as one incorrect switching operation per 100 million cycles at 17 V and 1 mA — important for low-energy signal switching where oxide films on contacts can cause intermittent faults. The mechanical endurance of 30 million operations is typical for a SIRIUS auxiliary contactor in cyclic service. Wire termination accepts 2x (0.25 to 2.5 mm²) solid or stranded conductors. The IP20 front protection means it is suitable for dry, enclosed panel environments but not for washdown or outdoor exposure.
Lifecycle and sourcing reality
The 3RH1122-2BM40 is the auxiliary contactor companion to Siemens SIRIUS contactors in size S00. If a panel was specified around a 3RT1015 contactor, this auxiliary contactor shares the same S00 footprint and mounting rail, so it drops in without rewiring the main power circuit. Verify the coil voltage of the main contactor separately — this listing is for the auxiliary block only.
Integration into the panel
At 45 mm wide, 60 mm tall, and 73 mm deep, this auxiliary contactor occupies a single 45 mm DIN-rail module. The depth of 73 mm means it clears most standard 80 mm deep enclosures, but check gland plate clearance if the panel is shallow. Shock resistance is 10g for 5 ms and 5g for 10 ms, covering most industrial vibration environments up to moderate shock. The operating temperature range of -25 to +60 °C covers typical indoor panel conditions.