What it is and where it fits
The Siemens 3RH1122-1AL00 is a SIRIUS auxiliary contactor in size S00 — the smallest frame in the SIRIUS family, designed for control-circuit switching rather than motor-load breaking. It carries 2 normally-open and 2 normally-closed instantaneous contacts, configurable for interlocking, status feedback, or logic-level signal routing inside a panel. Mounting is via screw or snap-on onto a DIN rail, and the front face is rated IP20, so it's safe for finger contact inside an enclosed panel but not for washdown environments. The size S00 footprint (45 mm wide, 57.5 mm high, 72 mm deep) slots into the same DIN-rail real estate as the matching S00 contactors and overload relays.
Contact ratings and what they mean for your circuit
Each contact is rated 10 A at 24 V, 6 A at 230 V, and 3 A at 400 V — these are the thermal (resistive) current ratings that govern continuous carry. For inductive DC loads the numbers drop sharply: 1 A at 110 V, 0.27 A at 220 V. That 0.27 A at 220 VDC is the figure to watch if you're switching DC solenoids or brake coils; the AC ratings don't apply there. Surge voltage withstand is 6 kV, which covers the impulse voltage expected in 400 V industrial environments (overvoltage category III). The contact reliability spec — one incorrect switching operation per 100 million operations at 17 V, 1 mA — means it's suitable for dry-contact PLC inputs where low-level switching is the norm.
Wiring and mechanical endurance
Terminals accept solid conductors from 0.5 mm² up to 4 mm², with two wires per clamp possible at the smaller sizes. That covers most control-circuit wiring from signal-level pairs to 4 mm² power feeds for the contactor coil itself. Mechanical endurance is rated at 30 million operations typical — the contactor itself will outlast most machines if the electrical load stays within the switching curves. Shock resistance is 10g at 5 ms and 5g at 10 ms, so it holds up on vibrating conveyor frames or packaging machinery.
Lifecycle and sourcing reality
Environmental compliance includes RoHS substance prohibition dated July 1, 2006, which covers the original EU RoHS directive. The pollution degree rating of 3 means it's designed for industrial environments with conductive or dry non-conductive pollution — standard for control panels not in clean rooms.