The Siemens 3RA1120-1FA23-0AK6 is a nonreversing combination starter from the SIRIUS family, frame size S0. It integrates a motor starter protector (MSP) and a contactor in one package, rated for 3.5-5 A with a 208 VAC control voltage. The MSP provides short-circuit and overload protection; the contactor handles the switching. No auxiliary contacts are fitted on either the MSP or the contactor side. Mounting is DIN rail or direct panel mount, which simplifies panel integration — the S0 footprint is compact enough for dense control cabinets. The unit is IEC-rated and carries UL file E156943 in volume 1, section 14, so it meets North American code requirements for motor branch circuits.
Frame size and fit
The physical envelope is consistent across S0 starters, so panel cutouts and DIN-rail spacing are standardised. If you are replacing an existing S0 starter or designing a new panel, the 3RA1120-1FA23-0AK6 drops into the same footprint.