What it is and what it does
The Siemens 3RH1122-1AK20 is a SIRIUS auxiliary contactor, size S00, designed to switch control circuits in motor starter and contactor assemblies. It carries two normally-open instantaneous contacts (2 NO) and no NC, delayed, or make-before-break switching — the contact complement is fixed at delivery. Rated surge voltage resistance is 6 kV, and the front face carries IP20 protection. Pollution degree 3 means it's rated for industrial environments with conductive pollution — no additional conformal coating required for typical panel conditions.
Switching ratings and what they mean for your circuit
The contactor's switching capacity varies with voltage and duty. At 24 V rated value it handles 10 A; at 230 V rated value, 6 A; at 400 V rated value, 3 A; and at 690 V rated value, 1 A. These are the maximum continuous currents the contacts can make and break at those voltages — derate further for inductive loads like relay coils or solenoid valves. Contact reliability is specified as one incorrect switching operation per 100 million operations at 17 V, 1 mA — that's the dry-circuit performance for PLC-level signals. Mechanical endurance is 30 million operations typical, which outlasts most panel lifecycles.
Mounting and integration into the panel
Fastening is by screw and snap-on mounting onto standard DIN rail. The S00 footprint is 45 mm wide, 57.5 mm high, 72 mm deep — fits the standard S00 slot in a SIRIUS motor starter assembly. Mounting position allows +/-180° rotation on a vertical surface and +/-22.5° tilt forward/backward, so orientation constraints are minimal. Terminals accept solid conductors: 2x (0.5 to 1.5 mm²), 2x (0.75 to 2.5 mm²), or 2x 4 mm². That covers most control wiring from signal-level to 4 mm² power feeds. Shock resistance is 10g / 5 ms and 5g / 10 ms — adequate for panel-mounted equipment in conveyor or machine-tool applications.