What this SIRIUS motor starter delivers
The Siemens 3RA2125-0KA23-0AP6 is a SIRIUS non-fused motor starter, built as a direct starter in Size S0, combining a contactor and a thermal bimetallic overload relay in one package. Rated at 370 W at 400 V (AC-3), it handles small motor loads like pumps, fans, and conveyors up to 0.5 hp at 460/480 V. The Class 10 trip characteristic means the overload relay opens within 10 seconds at 600% of the set current — fast enough to protect standard squirrel-cage rotors against locked-rotor heating.
Mounting and panel fit
Mounting position is vertical only. Width is 45 mm, depth 97.1 mm, height 193.1 mm. Clearance: 30 mm above, 10 mm below, 10 mm front, 9 mm side — plan your gland plate and busbar spacing accordingly. Main terminals accept 1…10 mm² stranded (2x 2.5…6 mm²) or 2x AWG 16…12 / 2x AWG 14…8 — wires up clean with a ferrule and a #2 Pozidriv.
Lifecycle and sourcing
The supplied contactor is 3RT2023-1AP60 and the link module is 3RA2921-1AA00 — both standard SIRIUS components, so spares and replacements are straightforward to source.