What it is and where it lands
The 3RH2140-1BF40-ZX95 is a Siemens SIRIUS auxiliary contactor block in size S00, carrying four instantaneous NO contacts and a 110 VDC-rated magnet coil. It screws or snaps onto 35 mm DIN rail, with a footprint of 45 mm wide by 58 mm tall by 73 mm deep — tight enough for crowded subpanels where every millimeter of rail space is spoken for. The product extension for an auxiliary switch is built in, so you can stack additional contact blocks on the same contactor without reworking the wiring tray.
What the ratings mean for fit
The coil draws 4 W during both closing and holding. The 110 VDC rated coil holds at 0.8 x rated and drops out above 1.1 x rated. Contact ratings are given per voltage: 10 A at 24 VDC and 230 VAC, 3 A at 110 VDC, 1.2 A at 220 VDC, dropping to 0.26 A at 600 VDC. The DC-12 operating frequency maxes out at 1,000 cycles per hour — that governs how fast you can cycle a DC load before the contacts need thermal recovery. Arcing time sits between 10 and 15 ms, with a DC arcing time of 7 to 13 ms. That matters for interlocking circuits where you need to guarantee the NC opens before the NO closes — the overlap window is tight, so sequence timers or mechanical interlocks are still the safer call for reversing starters.
Mounting and environment
Mounts on 35 mm DIN rail via the integrated snap-on latch, or screws directly to a backplate. The mounting position allows ±180° rotation on a vertical surface and ±22.5° tilt forward or backward, so it fits in control panels where the rail is angled or the door is hinged. Clearance requirements: 10 mm upward, 10 mm forward, 10 mm downward, 6 mm at the sides — no extra breathing room needed for arc flash containment, just standard segregation. Rated for pollution degree 3 (conductive pollution typical in industrial enclosures) and operates from -25 °C to +60 °C. Storage range is -55 °C to +80 °C — that's the shipping and shelf-life window, not the running band. Relative humidity floor is 10 %, so no special climate-controlled storage required for spares.