What it is and what it does
The Siemens 3RH1140-1BW40-0AA6 is a SIRIUS auxiliary contactor — a control-circuit relay designed to multiply the auxiliary contacts of a main contactor or to serve as a standalone signal interposer in a 48 V DC control loop. It carries 4 normally-open instantaneous contacts, each rated for 10 A at AC-12 (resistive) duty, so it handles pilot-duty loads like PLC inputs, indicator lamps, and small solenoid valves without a separate interposing relay.
Ratings that matter for fit
The 48 V DC coil draws 3.2 W during both pick-up and hold, which means the coil-supply transformer or power supply must be sized for that continuous draw — no inrush peak to worry about, but the steady-state load is constant. The contact ratings drop with voltage: at 110 V DC the contacts are rated for 1 A, at 220 V DC for 0.27 A, and at 690 V DC for 1 A, so the same contact block can switch a range of DC loads as long as the current stays within the curve. The contact reliability spec — one incorrect switching operation per 100 million operations at 17 V, 1 mA — tells you this contactor is comfortable switching dry logic-level signals, not just power loads. That matters when the auxiliary contacts feed a PLC input or a safety relay: you won't get nuisance failures from oxide films on the silver contacts.
Where it fits in the panel
Size S00 means it shares the same 45 mm width and 57.5 mm height footprint as the smallest SIRIUS contactors. It mounts via screw or snap-on onto a DIN rail, and the mounting position is flexible — it can be rotated ±180° on a vertical surface or tilted ±22.5° forward/backward, which helps when you're retrofitting into a crowded enclosure. The IP20 front protection means it's safe for finger contact in a closed panel but not for washdown environments. The terminal block accepts solid conductors from 0.5 mm² up to 4 mm², covering standard control wiring. Pollution degree 3 means it's rated for industrial environments with conductive dust or occasional condensation — typical for an unsealed panel in a factory.
Lifecycle and sourcing reality
The 3RH1140-1BW40-0AA6 is a control-circuit component with a 48 V DC coil. It sits alongside the 3RT10xx power contactors in a SIRIUS system.
Environmental and compliance
Rated for operation from -25 °C to +60 °C, with storage and transport range of -55 °C to +80 °C. Surge voltage resistance is 6 kV. RoHS compliance date is listed as July 1, 2006, meaning the design predates the EU RoHS directive but the part is manufactured to comply. No explicit UL or CSA listing is in the evidence, so verify with your local Siemens representative if the installation requires those marks.