What this auxiliary contactor is and where it fits
The Siemens 3RH1122-1KF40-0LA4 is a SIRIUS auxiliary contactor in the size S00 frame, designed to switch control circuits and signal loads in motor control centers and panel builds. It provides 2 normally open and 2 normally closed instantaneous auxiliary contacts, with no delayed, lagging, or make-before-break switching functions — a straightforward 4-pole block for feedback or interlock duties. The 45 mm width and 57.5 mm height fit standard DIN-rail spacing, and the 72 mm depth leaves room for wiring in shallow enclosures. Screw and snap-on mounting means it clips onto the rail without tools but can also be screw-fixed for vibration-prone installations.
Rated switching capacity and what it means for your circuit
The AC-12 maximum operating current is 10 A, which covers resistive control loads like contactor coils and indicator lamps. At 24 V the contacts are rated for 10 A, at 110 V for 1 A, at 230 V for 6 A, at 400 V for 3 A, at 500 V for 2 A, and at 690 V for 1 A — these are the current limits per pole at those voltages, so the actual load determines which rating applies. The coil is 110 V rated and includes a built-in varistor surge suppressor, which suppresses voltage spikes from the inductive coil when de-energized. Closing power is 11 W DC, holding power 4 W DC — the lower holding draw means the coil runs cooler once sealed.
Environmental limits and mounting flexibility
Operating temperature range is -40 to +70 °C, storage and transport from -55 to +80 °C, so it handles both cold storage and warm panel conditions. Pollution degree 3 means it's rated for industrial environments with conductive pollution or dry non-conductive pollution that becomes conductive due to condensation — typical for unsealed control panels. Mounting position allows +/-180° rotation on a vertical surface, and can be tilted forward or backward by +/-22.5° on a vertical surface — useful when the contactor must sit at an angle in a crowded cabinet. Side clearance is 0 mm, so units can be mounted flush side-by-side without derating for heat buildup. Shock resistance is 10g for 5 ms and 5g for 10 ms, which covers most industrial vibration from contactors and starters in the same panel. Maximum operating altitude is 2 000 m without derating.
Wiring and terminal capacity
The terminals accept solid conductors: 2x (0.5 to 1.5 mm²), 2x (0.75 to 2.5 mm²), and 2x 4 mm². This covers standard control wiring from signal-level to power-feed sizes, and the dual-conductor capacity allows looping through without a separate terminal block. IP20 on the front means finger-safe from the front face, but the contactor is not sealed against dust or moisture ingress — it belongs inside a panel with at least IP54 enclosure protection.