What it is and what it does
The Siemens 3RH1344-1BM40-ZX95 is a SIRIUS auxiliary contactor in size S00, built to switch control circuits rather than motor loads directly. It carries 4 instantaneous normally-open contacts and is rated for a 220 V AC coil. This is the part you add to a main contactor or use standalone to multiply signal paths in a panel — think PLC output isolation, interlocking, or status feedback to a DCS.
Key ratings and what they mean for fit
The 4 NO contacts are rated for switching at various control voltages: 10 A at 24 V, 6 A at 230 V, 3 A at 400 V, and 1 A at 690 V. That derating curve tells you the contacts are silver-alloy and handle resistive loads well — at 24 VDC you get full 10 A, but at 690 V AC the arc limits you to 1 A. For a 24 VDC PLC output interposing relay, this contactor comfortably handles a dozen small solenoids or indicator lamps in parallel. The coil draws 3.2 W closing and holding power at DC. Surge voltage resistance is rated at 6 kV. Mechanical endurance is 10 million operations typical, and contact reliability is specified as one incorrect switching operation per 100 million at 17 V, 1 mA — that low-level switching spec matters if you're routing dry-contact signals to a PLC input card where oxide films on standard contacts can cause intermittent faults.
Mounting and integration
Mounting is via screw and snap-on. The size S00 footprint is 45 mm wide, 57.5 mm tall, 111 mm deep. The mounting position is flexible: +/-180° rotation on a vertical surface, and can be tilted forward/backward by +/-22.5°. That's useful when you're fitting it into a tight corner of a panel and the DIN rail isn't perfectly vertical. The IP20 front protection means it's touch-safe on the front but not sealed against dust ingress — standard for inside an enclosure. Wire terminations accept solid conductors: 2x (0.5...1.5 mm²), 2x (0.75...2.5 mm²), or 2x 4 mm². For AWG, that's 2x (20...16), 2x (18...14), or 1x 12. The spring-cage or screw terminals (not specified in evidence, but typical for this series) handle ferruled stranded as well. Shock resistance is 10g/5 ms and 5g/10 ms — fine for most industrial machinery but not rated for continuous high-vibration applications like crushers.