What this compact starter is and why the trip class matters
The Siemens 3RA6120-1EB34 is a SIRIUS compact starter — a direct-on-line (DOL) starter that combines a contactor and overload relay in a single 45 mm wide housing. The trip class is adjustable between CLASS 10 and CLASS 20, which means you can match the thermal overload curve to the motor start profile. CLASS 10 trips faster — suited for short acceleration times like pumps or fans — while CLASS 20 allows longer inrush for high-inertia loads such as conveyors or centrifuges. Getting this wrong on a DOL starter causes nuisance tripping or missed protection.
Coil voltage and control wiring
The coil is rated 24 V AC/DC, 50/60 Hz, drawing 3.5 W AC maximum or 3.1 W DC maximum. That means a single 24 V supply — either a control transformer or a DC power supply — runs the starter, and the power draw is low enough that multiple units can share a small supply without oversizing. Screw-type terminals on the main circuit accept solid conductors from 0.5 to 4 mm², and two conductors per clamp (0.5 to 2.5 mm²) are allowed for daisy-chaining control wiring. This is a standard panel-building detail: the terminal capacity matches typical motor-circuit wire sizes up to 4 mm², so no adapter or ferrule change is needed.
Environmental and mounting notes
Mounting position is any orientation, though the recommended installation is vertical on a horizontal DIN rail.