What It Is & What It Does
The 3RH1122-2KB40-1AA0 is a Siemens SIRIUS auxiliary contactor in size S00, designed to switch control circuits rather than motor loads — it extends the contact count of a main contactor or provides isolated signal feedback to a PLC. It carries 4 normally-open and 2 normally-closed instantaneous contacts, all rated for 10 A at 24 V, with a contact reliability of one incorrect operation per 100 million cycles at 17 V, 1 mA — meaning it's dependable for low-energy PLC inputs without wetting current issues. The 24 V DC coil draws 11 W on pickup and holds at 4 W, so it's compatible with standard 24 VDC control supplies and doesn't overload a small power supply on sustained hold.
Mounting & Integration
Mounts via screw or snap-on to a DIN rail, standing on a horizontal surface — the 45 mm width and 60 mm height fit the standard S00 footprint, so it drops into any panel already laid out for SIRIUS contactors without re-drilling. Depth is 73 mm, which leaves clearance behind the DIN rail for wiring; the spring-cage terminals accept 0.25 to 2.5 mm² solid or ferruled stranded wire, so no special crimp tooling is needed for standard control wiring. IP20 on the front means it's protected against finger contact but not washdown — keep it inside a closed panel, not on the machine frame in a wet area.
Contact Ratings & Application
The contacts are rated for switching at multiple voltages: 10 A at 24 V, 6 A at 230 V, 3 A at 400 V, 2 A at 500 V, and 1 A at 690 V — these are the thermal current ratings for the contact block, so they handle control transformer secondaries and PLC output loads across common line voltages. Built-in varistor surge suppression across the coil handles the inductive kick from the DC coil, so you don't need an external flyback diode — just wire the coil and go. Rated surge voltage resistance is 6 kV, and pollution degree 3 means it's suited for industrial environments with conductive dust or occasional condensation inside the panel.
Environmental & Compliance
Operating temperature range is -25 to +60 °C, with storage and transport from -55 to +80 °C — so it's fine for unheated warehouses and shipping containers in winter. Shock resistance is 10g for 5 ms and 5g for 10 ms, which covers most vibration from contactors and breakers in the same panel. RoHS compliance date is July 1, 2006 — the part meets the original RoHS directive, which is the standard for most industrial equipment sold today.