What it is and where it fits
The Siemens 3RH1140-1BB40-ZW96 is a SIRIUS auxiliary contactor — a 4-pole, 24 V DC coil device with 4 NO instantaneous contacts, rated 10 A at 24 V. It's built for the S00 contactor frame size, so it shares the 45 mm width and 57.5 mm height of the SIRIUS 3RT1 power contactors, with a 72 mm depth that clears the standard DIN-rail enclosure depth.
Key ratings and what they mean for fit
The 24 V DC coil draws 3.2 W for both closing and holding power — a constant DC draw that simplifies power supply sizing in a control panel. The 4 NO contacts are rated for switching at multiple voltages: 10 A at 24 V, 6 A at 230 V, 3 A at 400 V, down to 1 A at 690 V. This means the contactor handles signal-level loads (PLC outputs, pilot devices) through to moderate auxiliary circuits in motor starter buckets, as long as the load current stays under the voltage-specific curve. Contact reliability is specified at one incorrect switching operation per 100 million operations at 17 V, 1 mA — a dry-circuit rating that matters for low-energy signal paths where oxide films on silver contacts can cause intermittent opens. For a Tier-1 line running 24 V PLC inputs, this means the contactor won't introduce nuisance faults on low-level signals.
Mounting and wiring constraints
Mounting is screw or snap-on onto 35 mm DIN rail. The mounting position allows ±180° rotation on a vertical surface and ±22.5° tilt forward/backward — useful when the contactor sits on a swing-panel or a gland-plate bracket. Wire termination accepts 2x (0.5 to 1.5 mm²), 2x (0.75 to 2.5 mm²), or 2x 4 mm² solid, or the AWG equivalents (2x 20-16, 2x 18-14, 1x 12). The IP20 front protection means it's safe for finger contact inside an enclosed panel, but not for washdown or outdoor exposure.