What it is and where it fits
The Siemens 3RH2140-1BB40-ZX95 is a SIRIUS auxiliary contactor in frame size S00 — a compact 45 mm wide, 57.5 mm tall, 73 mm deep block that screws or snaps onto 35 mm DIN rail. It carries four normally-open instantaneous contacts, coil rated 24 VDC with a closing and holding power draw of 4 W. This is the part you reach for when a contactor or starter needs extra signal contacts, or when you're building a dedicated interlock chain in a control panel.
Contact ratings — what the numbers mean
The contacts are rated for 10 A at 230 V AC (resistive) and 10 A at 24 V DC. At higher DC voltages the current drops sharply — 4.7 A at 60 V, 1.2 A at 220 V, 0.26 A at 600 V — because DC arcs are harder to extinguish. For AC inductive loads the curve is gentler: 3 A at 400 V, 1 A at 690 V. The mechanical life is 30 million operations typical, and the contactor can switch at 10,000 cycles per hour AC. Arcing time runs 10 to 15 ms. That's the spec-sheet story; the real-world takeaway is that this is a signal-duty block, not a power-switching device — use it for control circuits, PLC inputs, auxiliary relays, and contactor coils, not for motor loads directly.
Mounting and integration
Mounts on 35 mm DIN rail via the integrated snap-on latch, or with screws through the base. The mounting position is flexible: ±180° rotation on a vertical surface, and can be tilted forward/backward by ±22.5°. Clearance distances are tight — 10 mm upwards, forwards, and downwards, 6 mm at the sides — so you can pack these side-by-side in a panel without derating. Wire termination accepts 2x 0.5 to 1.5 mm² solid/stranded, 2x 0.75 to 2.5 mm², or 2x 4 mm². Pollution degree 3 means it's rated for the usual industrial panel environment with conductive dust and occasional condensation.