Integrator note: what the ratings mean for fit
The Siemens 3RH1122-2BD40 is a SIRIUS auxiliary contactor in size S00, rated for a 42 V DC coil. The 10 A AC-12 rating covers resistive and lightly inductive loads typical for control-circuit switching — think PLC outputs, pilot lights, or small contactor coils. The 42 V DC coil pull-in and hold power is 3.2 W, so the control transformer or DC supply must be sized for that continuous draw; a 24 V DC supply won't pull this contactor in. The 6 kV rated surge voltage resistance means it's designed for industrial environments with moderate transient energy, not just clean office power.
Panel integration and mounting
Mounts via screw or snap-on onto a DIN rail. The 45 mm width and 73 mm depth fit the standard S00 footprint — leaves room for adjacent contactors or terminals in a crowded panel.
Wiring and contact configuration
Solid (ferruled or solid) conductors from 0.25 to 2.5 mm² are accepted. The contactor carries 2 instantaneous contacts and no delayed or make-before-break contacts. Contact reliability is rated at one incorrect switching operation per 100 million operations at 17 V, 1 mA — good for dry-circuit switching into PLC inputs or low-energy loads. The auxiliary switch extension is available as an add-on, so you can field-upgrade contact count without swapping the base unit.
Environmental and compliance
Operates from -25 to +60 °C; storage and transport range is -55 to +80 °C. Shock resistance is 10g / 5 ms and 5g / 10 ms — sufficient for normal industrial vibration but not for high-shock applications like stamping presses. Pollution degree 3 means it's rated for conductive pollution environments (condensation, occasional conductive dust). RoHS compliance is indicated by the substance prohibitance date of 07/01/2006.