What it is and what it does
The Siemens 3RH1344-1TP00-0KV0 is a SIRIUS auxiliary contactor, size S00, with four normally-open instantaneous contacts. It's designed to switch control signals and auxiliary loads in motor control centers and panel builds — think signaling the PLC that a main contactor has picked up, or interlocking a sequence. The 4 NO contacts are rated 10 A at 24 V, 6 A at 230 V, and 1 A at 690 V, which covers most control-circuit voltages you'll find in a 400 V panel. Contact reliability is specified at one incorrect operation per 100 million switching operations at 17 V, 1 mA — that's gold for dry-circuit PLC inputs where oxidation can cause nuisance failures.
Mounting and integration
Mounts via screw or snap-on onto DIN rail. The S00 footprint is 45 mm wide by 57.5 mm high by 111 mm deep — tight enough for dense panels. Mounting position is flexible: +/-180° rotation on a vertical surface, and can be tilted forward/backward by +/-22.5°. Wire termination accepts 2x 0.5–1.5 mm², 2x 0.75–2.5 mm², or 2x 4 mm² solid. The IP20 front means it's protected against finger contact — standard for inside a cabinet, but don't hose it down.
Lifecycle and sourcing
Surge suppression is built in via a varistor across the coil terminals. That saves you an external suppressor module and the labor to wire it — one less thing to forget on a midnight startup.