The Siemens 3RH1140-1KB40 is a SIRIUS coupling relay — a compact auxiliary contactor designed to switch control and signal circuits in industrial panels. It carries 4 normally-open instantaneous contacts rated 10 A at 24 V, with a 24 VDC coil drawing 2.3 W both on pickup and hold.
For inductive loads like small contactor coils or solenoid valves, derate per the AC/DC switching curves: at 230 V AC the contacts are rated 6 A, at 400 V AC it drops to 3 A, and at 690 V AC it is 1 A. The part is built for that regime. A built-in varistor surge suppressor is integrated across the coil, so no external flyback diode is needed for DC switching. The coil holds at 24 VDC nominal; the 0.7 initial value and 1.25 full-scale value refer to pickup/dropout voltage thresholds relative to rated voltage. Shock resistance is 10g at 5 ms and 5g at 10 ms — adequate for most industrial panel environments but not for direct machine-mount on high-vibration equipment.
The 3RH1140-1KB40 is the coupling relay variant; the functionally similar 3RT1015 series contactors share the same S00 frame and mounting footprint but lack the varistor and are intended for motor switching rather than auxiliary circuit isolation.
Integration notes
Wire termination accepts solid conductors: 2x 0.5 to 1.5 mm², 2x 0.75 to 2.5 mm², or 2x 4 mm² — screw terminals. Dimensions are 45 mm wide, 57.5 mm tall, 72 mm deep — fits standard DIN-rail enclosures with 45 mm per module spacing. The depth of 72 mm means it will clear most 80 mm deep enclosures but check against shallow 60 mm boxes. The part carries a reference code K per IEC 81346-2 (relay/contactor function) and RoHS compliance date of July 1, 2006, indicating it meets EU substance restrictions.